Lemon-Vanilla Angel Food Cake with Raspberry-Blueberry Sauce

Raspberry-Blueberry Sauce
2 cups fresh or unsweetened frozen raspberries
1/3 cup raspberries preserves or jam
1/3 cup water
2 tablespoons granulated sugar
1 cup fresh or frozen blueberries (small berries work better here)

Lemon-Vanilla Angel Food Cake
1 1/2 cups egg whites
Butter to grease pan (if using a pan without a removable bottom)
1 cup all-purpose flour, or 1 1/4 cups cake flour
1 cup granulated sugar, or 2 cups confectioners