Freedom Cake
A freedom cake is a dessert baked in the United States on or around the 4th of July Independence Day holiday. It can be a cake of any sort, decorated with white frosting on top, accompanied by blueberries arranged in a square on the top left corner and horizontal rows of strawberries or red raspberries running across the remainder of the cake's surface. This configuration depicts the American flag, hence the name.
Jane didn't know what to bring to the 4th of July picnic until her mother suggested baking a Freedom Cake in order to make use of the blueberries and strawberries they had just bought.