S.C.
This is a favorite with my family:
Buy a box of strawberry cake mix and prepare as directed (bake in 2 round pans). When it has cooled, cover the bottom layer with strawberry jam, 1/2 a container of cool whip and blueberries. Put the 2nd layer on top and repeat with the strawberry jam, and remaining cool whip. Garnish the top with blueberries and strawberries. I have found that using an egg slicer to slice strawberries works well - then I fan the slices out on top of the cake.
My cousin dubbed the cake "heavenly, glorious cake" and when I make it, there are no leftovers!
Hope you have a great 4th of July party!!