I tend to take my holiday traditions very seriously. Thanksgiving Day always begins with the "Oh You Turkey Coloring Contest" in the Minneapolis-St. Paul paper. (Never mind that I aged out of the competition approximately 20 years ago.) Christmas and Hanukkah presents must be opened one at a time, going in ascending order from youngest to oldest. My birthday has been celebrated with a hot dog for 27 years and counting (long story). And the 4th of July means two things: my Fourth of July skirt (blue with white stars) and a red white and blue dessert. For the last couple of years this has meant Dorie Greenspan's Perfect Party Cake, slathered in white buttercream and adorned with red and blue berries. This year, I decided to take things a step further and blend pureed berries into the batter in order to turn the cake layers red white and blue. Truth be told, my cake was closer to pink, white and periwinkle than red white and blue, but I didn't mind. It still felt festive, and as an added bonus, it was filled with subtle berry flavor rather than freaky food colorings. I think we have a new tradition in the making.
Red White and Blue Cake
For the Cake
Adapted from Dorie Greenspan's Perfect Party Cake from Baking From My Home to Yours
2 cups all purpose flour*
1 tablespoon baking powder
1/2 teaspoon salt
1 1/4 cups buttermilk
4 egg whites
1 1/2 cups sugar
1 stick unsalted butter, at room temperature
1/2 teaspoon vanilla extract
1 cup strawberries
1 cup blueberries
3 tablespoons water
*Note: The original recipe for the Perfect Party Cake calls for 2 1/4 cups cake flour. Since I didn't have any cake flour on hand, I substituted with a lesser amount of all-purpose flour. I haven't tested this version with cake flour, but it will likely produce a lighter cake with a more delicate crumb. If that's what you're after, it may be worth using 2 1/4 cups cake flour here instead of 2 cups of all-purpose. My all purpose version was denser and almost banana-bread-like.
Preheat the oven to 350. Butter three 9-inch round cake pans and line the bottoms with parchment paper. Puree the strawberries in a blender or food processor, and set aside. Combine the blueberries and 3 tablespoons water in a small saucepan. Cook over medium heat until the blueberries have released their juices and the mixture is deep blue and bubbling. Set a sieve or strainer over a bowl and carefully pour the blueberries over it, reserving the liquid. Discard the berries.
Sift the flour, baking powder and salt into a bowl and set aside. In a separate bowl, stir together the egg whites and buttermilk and set aside as well. In the bowl of a stand-mixer fitted with the paddle attachment, beat the butter and sugar until light and fluffy, about three minutes. Beat in the vanilla extract. With the mixer running, add in 1/3 of the flour mixture, followed by 1/2 of the buttermilk mixture. Continue alternating the flour and milk, adding another 1/3 of the flour mixture, the remaining buttermilk, and then the rest of the flour. Scrape down the sides of the bowl if necessary, and then beat the batter on medium for about a minute to make sure it's well incorporated.
Remove 2/3 of the batter from the mixer and set aside. Add a few tablespoons of strawberry puree to the remaining 1/3 of the batter, and mix on low until combined. Continue adding strawberry puree a few tablespoons at a time until your batter is the desired color. You will not need all of the puree. Transfer the pink batter to one of the prepared baking pans. Wipe out the bowl of the stand mixer, and put another 1/3 of the batter back into the bowl. With the mixer on low, drizzle in some of the blueberry juice, slowly adding more until it's the desired color. You will not need all of the blueberry juice. Transfer the blue batter to one of the prepared baking pans. Transfer the remaining 1/3 of white batter to the final baking pan.
Bake for about 30-35 minutes, or until the edges of the cake are golden, it's springy to the touch, and a tester inserted in the center of the cakes comes out clean. Allow the cakes to cool in the pans for about 10 minutes, then run a knife around the edges, invert onto wire racks, and peel off parchment paper. Allow the cakes to finish cooling completely.
For the Frosting
3 cups heavy cream
1/3 cup powdered sugar
1/2 teaspoon vanilla extract
Combine the cream and the vanilla extract in the bowl of a stand mixer. Using the whisk attachment, beat on medium, adding the powdered sugar a little at a time. Turn the mixer to high, and beat until stiff peaks form. Taste the frosting and add a bit more sugar if desired. Use the frosting immediately, or keep it cool in the refrigerator.
To Assemble the Cake
Place the blue layer on a cake stand or cake board. Top with a large dollop of whipped cream, and use a spatula to spread the whipped cream almost to the edges. Place the white cake layer carefully over the blue layer. Spread a dollop of whipped cream over the white layer, and top with the red layer. Spread the rest of the whipped cream over the top and sides of the cake, using an offset spatula if you have one. Serve the cake immediately, or store in the refrigerator for a few hours until ready to eat.
To Decorate the Cake
I decorated my cake with a red white and blue banner, which I made by following these instructions from Joy the Baker.