Red, White, and Blue Trifle

Preheat the oven to 350 degrees F (175 degrees C). Grease a 9x9-inch glass baking pan.

Beat eggs until very light, about 3 minutes. Add sugar and butter. Sift flour, baking powder, and salt together. Add to the egg mixture in batches, alternating with milk, beating batter briefly after each addition. Pour into the prepared pan.

Bake in the preheated oven until a toothpick inserted into the cake comes out clean, 30 to 35 minutes. Let cool completely.

In the meantime, make the custard. Whisk sugar, flour, and salt together in a saucepan over low heat. Add milk and eggs. Cook, stirring frequently, until custard thickens, about 25 minutes. Remove from heat and add butter and vanilla extract. Store custard in a glass container in the refrigerator until ready to use.

Combine cream and sugar; whip until stiff peaks form. Set aside in the refrigerator.

Cut the cake into 2- or 3-inch squares. Place a layer of cake on the bottom of a trifle dish. Add enough custard to cover the cake. Add a layer of strawberries and a layer of blueberries. Cover with some of the whipped cream. Top with another layer of cake. Repeat until the final layer is either custard or whipped cream. Arrange remaining berries decoratively on top.

Cover trifle with plastic wrap and chill until ready to serve, at least 30 minutes.