There is something undeniably comforting about a recipe that has stood the test of time, especially when it involves the ease of a simple box mix hack. I remember seeing this bright green cake at potlucks growing up, always wondering about the fun name and the fluffy, cloud-like topping. It is one of those “mix and bake” miracles that proves you do not need a culinary degree to put a spectacular dessert on the table.
This cake is famously moist, thanks to the crushed pineapple and instant pudding right in the batter, giving it a texture that is truly silky and tender. With its pastel green hue and crunch of pecans, it is a conversation starter that tastes as good as it looks. Best of all, it comes together in just one bowl with minimal cleanup, making it a perfect candidate for a busy weeknight treat or a weekend gathering.
A Retro Classic That Is Pure Joy
There are so many reasons to keep this recipe in your back pocket. First, it is the definition of low effort, high reward. By starting with a boxed white cake mix, we skip the measuring and sifting of dry ingredients, jumping straight to the flavor. The addition of instant pistachio pudding mix and crushed pineapple transforms that humble box into something rich, dense, and incredibly moist.
You will also love how versatile this cake is. While it is perfect for St. Patrick’s Day or Easter with its lovely green color, the flavors of pineapple, coconut, and pistachio are delicious year-round. The “cover-up” frosting—a simple blend of whipped topping and pudding—is light and airy, providing the perfect contrast to the tender crumb beneath. It is a nostalgic slice of happiness that tastes like a sweet memory.
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Watergate Cake
- Total Time: 2 hours 50 mins
- Yield: 15 servings
- Diet: Vegetarian
Description
A nostalgic, vibrant green dessert that combines the ease of a boxed cake mix with the tropical flavors of crushed pineapple, coconut, and crunchy pecans. This moisture-rich cake is topped with a light and fluffy pistachio-infused frosting, making it a crowd-pleasing classic for any celebration.
Ingredients
- 1 (15.25 oz) box white cake mix
- 2 (3.4 oz) boxes instant pistachio pudding mix, divided
- 1 (20 oz) can crushed pineapple, juice reserved
- 1/2 cup vegetable oil
- 1/2 cup milk
- 3 large eggs
- 1 cup chopped pecans, divided
- 1 cup sweetened coconut flakes, divided
- 1 (8 oz) container whipped topping, thawed
- 1 cup mini marshmallows
Instructions
- Preheat your oven to 350°F (175°C) and grease a 9×13-inch baking dish with non-stick spray.
- Drain the crushed pineapple through a fine-mesh sieve into a bowl, pressing with a spoon to reserve exactly 1/2 cup of juice for the frosting.
- In a large mixing bowl, combine the dry white cake mix, one box of pistachio pudding mix, vegetable oil, milk, and eggs; beat with a hand mixer on medium for 2 minutes.
- Gently fold in the drained crushed pineapple, 3/4 cup of chopped pecans, and 3/4 cup of coconut flakes until evenly distributed.
- Pour the batter into the prepared pan and bake for 30 to 40 minutes, or until a toothpick inserted in the center comes out clean.
- Remove the cake from the oven and let it cool completely on a wire rack.
- To make the frosting, whisk the second box of pistachio pudding mix with the reserved 1/2 cup of pineapple juice until thick and smooth.
- Fold the thawed whipped topping and mini marshmallows into the pudding mixture until well combined.
- Spread the frosting over the cooled cake and garnish with the remaining 1/4 cup pecans and 1/4 cup coconut flakes.
- Refrigerate the cake for 1-2 hours to allow the topping to set before serving.
Notes
Store any leftover cake in the refrigerator in an airtight container for up to 3 days to maintain the freshness of the whipped topping. For a festive look, you can add a few drops of green food coloring to the batter if you want an even more intense pastel hue.
- Prep Time: 15 mins
- Cook Time: 35 mins
- Category: Dessert
- Method: Baking
- Cuisine: American
Simple Pantry Staples
One of the best things about this recipe is that it relies on ingredients you can easily find at any grocery store. Here is what you need to gather:
- White Cake Mix: The sturdy base of our cake. Grab your favorite 15.25-ounce box; any brand works well here to give us a head start.
- Instant Pistachio Pudding Mix: You will need two boxes—one for the cake batter (3.4 oz) and one for the topping. This provides that signature green tint and lovely nutty flavor.
- Crushed Pineapple: This is the secret to the cake’s moisture. Buy a 20-ounce can and save the juice! We use the fruit in the cake and the juice in the frosting.
- Vegetable Oil: keeps the cake tender and moist for days.
- Milk: Adds richness to the batter.
- Eggs: You can use 3 whole large eggs for richness, or just the whites if you want to keep the cake color lighter.
- Pecans: Finely chopped pecans add a wonderful crunch that contrasts with the soft cake. You’ll need some for the batter and the topping.
- Sweetened Coconut Flakes: Adds a chewy texture and tropical sweetness that pairs perfectly with the pineapple.
- Whipped Topping: A tub of Cool Whip (thawed) serves as the base for our fluffy frosting.
- Mini Marshmallows: Folded into the topping for extra sweetness and texture.
The Simple Process
Step 1: Prep and Organize
Preheat your oven to 350°F (175°C). Spray a standard 9×13-inch baking dish generously with non-stick cooking spray. Place a fine-mesh sieve over a bowl and drain the crushed pineapple. Press down with the back of a spoon to extract the juice—you need to reserve exactly 1/2 cup of juice for the frosting later.
Step 2: Mix the Batter
In a large mixing bowl, combine the dry white cake mix, one box of the dry pistachio pudding mix, vegetable oil, milk, and eggs. Beat with a hand mixer on medium speed for about 2 minutes until smooth. Stop to scrape down the sides of the bowl to ensure everything is incorporated.
Step 3: Fold in the Flavor
Using a spatula or wooden spoon, gently fold in the drained crushed pineapple, 3/4 cup of chopped pecans, and 3/4 cup of coconut flakes. Stir just until these ingredients are evenly distributed throughout the green batter. Pour the batter into your prepared pan and spread it out evenly.
Step 4: Bake to Perfection
Bake in the preheated oven for 30 to 40 minutes. You’ll know it is done when a toothpick inserted into the center comes out clean or with just a few moist crumbs. Remove the cake from the oven and place the pan on a wire rack. Let the cake cool completely before frosting; this is crucial so the topping doesn’t melt.
Step 5: Make the Topping
While the cake cools, make the frosting. In a medium bowl, whisk together the second box of instant pistachio pudding mix and the reserved 1/2 cup of pineapple juice. It will be thick and green. Gently fold in the thawed whipped topping until the color is uniform. Then, fold in the mini marshmallows.
Step 6: Frost and Chill
Spread the fluffy green mixture over the cooled cake. Sprinkle the top with the remaining chopped pecans and coconut flakes for garnish. Place the cake in the refrigerator for at least 1-2 hours before slicing to let the topping set.
Meagan’s Easy Baking Tips
- Drain Well: The most critical step is draining that pineapple. If you leave too much juice in the fruit, the cake can become too wet or dense. Really press it against the strainer.
- Don’t Overmix: When folding in the nuts, coconut, and fruit, use a gentle hand. Overworking the batter can lead to a tougher cake, and we want to keep this simple chocolate wacky cake level of tenderness.
- Cool Whip Consistency: Ensure your whipped topping is fully thawed in the fridge before using. If it’s frozen, it won’t mix smoothly with the pudding paste.
- Make Ahead: This cake actually tastes better the next day! The flavors meld together, and the moisture from the pineapple softens the coconut and nuts perfectly. It’s a great dessert to make on a Saturday for a Sunday dinner.
Make It Your Own
- Nut-Free Option: If you are baking for someone with a nut allergy (and they can tolerate the artificial flavoring in the pudding), simply omit the pecans. You can add extra marshmallows or even white chocolate chips for crunch.
- The “Bundt” Twist: You can bake this in a bundt pan for a more elegant presentation. Grease the pan very well and bake for 45-55 minutes, checking for doneness. Note that the frosting might need to be spooned over like a thick glaze or served on the side.
- Cherry on Top: For a pop of color that screams “vintage,” garnish each slice with a maraschino cherry. It adds a lovely contrast to the green.
- Cupcake Version: Divide the batter into lined muffin tins. Bake for 18-22 minutes. This is great for parties, similar to how we serve our vintage cake recipes at gatherings.
Everyday Enjoyment
This cake is rich and sweet, so I love serving it simply. A cold square straight from the fridge is refreshing on a warm day. It pairs beautifully with a hot cup of black coffee to balance the sweetness or a tall glass of cold milk.
If you are hosting a party, cut the squares a bit smaller—it is surprisingly filling! The bright green color makes it a fantastic addition to Easter brunch spreads or St. Patrick’s Day festivities. Just like our banana pudding poke cake, this is a dessert that thrives on being made ahead of time, freeing you up to enjoy your guests.
Keep It Simple
I hope this recipe brings a little bit of vintage charm to your kitchen. There is a reason these “back of the box” style recipes have survived for decades—they deliver honest flavor without the stress. Whether you call it Watergate Cake, Pistachio Cake, or just “that green cake,” it is sure to become a requested favorite.
For more easy, one-pan desserts, be sure to try our 3 ingredient dump cake. And if you are looking for even more variations on this classic, I’ve seen wonderful versions on sites like The Country Cook that are worth checking out.
Happy baking!
