2 cups blackberries
1/4 cup sugar
Zest and juice of 1 lemon
Nonstick cooking spray
2 cups (1 pint) vanilla ice cream, softened at room temperature
4 cups (2 pints) raspberry sorbet, softened at room temperature
One 15-ounce angel food cake, cut into 1/2-inch thick slices
4 large egg whites, room temperature
Pinch cream of tarter
2/3 cup sugar