Festive 4th of July Dessert

Cake:

Nonstick cooking spray, for the pan

2 1/2 cups all-purpose flour

1/3 cup stone-ground white cornmeal

1 teaspoon baking powder

1 teaspoon baking soda

1/2 teaspoon kosher salt

2 cups granulated sugar

2 sticks (1 cup) unsalted butter, at room temperature

5 large eggs, at room temperature

1 tablespoon pure vanilla extract

1 cup buttermilk

3 tablespoons rainbow or red, white and blue sprinkles

Frosting:

3 sticks (1 1/2 cups) unsalted butter, at room temperature  

1/4 teaspoon kosher salt  

3 ounces chopped white chocolate, melted and cooled slightly   

6 cups confectioners’ sugar  

1 1/2 teaspoons pure vanilla extract

Garnish:

1 cup blueberries

One 16-ounce container strawberries

1 tablespoon apple jelly or apricot jam, melted