If you like, make a curd with the left over egg yolk and serve with the angel food cake.
ingredients
Angel Food Cake
Blackberry Sauce
directions
Preheat oven to 350 degrees F.
Sift the flour, ½ cup sugar and the salt into a medium bowl. Add the zest and toss to combine.
Using a stand mixer or electric hand mixer, beat egg whites until frothy. Add the cream of tartar. Continue to beat on high until soft peaks begin to form. Very gradually, add the remaining 1 cup sugar. Continue to beat until meringue is glossy and stiff. Add the vanilla. Gently fold the flour mixture into the meringue until well blended, ensuring that you scrap the bottom of the bowl as you fold.
Pour into 10-inch ungreased tube pan. Bake until golden and middle springs back when touched, about 45 minutes. Invert onto the neck of a bottle. Cool completely upside down.
When cake is completely cooled, run a knife around the edge of the pan and along the tube. Invert on a cake plate or platter. Serve 10 to 12 servings.
Purée blackberries in a food processor and pass through a sieve. Mix blackberry puree with sugar and liqueur. Stir until combined.