Preheat oven to 350 degrees. Grease and flour three 9-inch round cake pans.
In a medium bowl, whisk together flour, baking powder and salt; set aside.
In a large bowl, beat butter and sugar until light and fluffy. Beat in eggs one at a time, then stir in vanilla.
Alternately add flour mixture and milk to butter mixture, beating on low speed after each addition until combined. Divide batter evenly among prepared pans.
Bake 25 to 30 minutes, or until a toothpick inserted into center of a cake comes out clean. Cool on wire racks.
To assemble cake, spread raspberry jelly between the first and second layer, and blueberry jelly between the second and third layer. Place top layer upside down on cake.
In a medium bowl, beat cream until stiff peaks form. Gradually add confectioners' sugar, beating until thick and spreadable.
Frost top and sides of cake with whipped cream. Decorate top of cake with remaining jelly to resemble an American flag.
Interesting Facts
Flag cake is traditionally made with raspberry and blueberry jellies.
This cake originated in the United States in the late 1800s.
This cake is often served at Fourth of July celebrations.