In a large mixing bowl with an electric mixer, beat egg whites until foamy. Add ¾ cup sugar, vanilla, salt and baking powder, beat until smooth and fluffy. Add flour and blend well. Stir in 1 cup tart cherries and chopped nuts. Pour into a greased 8-inch pie pan.
Bake in a preheated 350° F. oven for 30 minutes.
In medium saucepan combine 1 cup water, remaining ½ cup pitted cherries, remaining ¾ cup sugar and cornstarch. Cook over medium heat until thick and bubbly. Add coloring, if desired; keep sauce warm.
Cut cake into wedges. Top each wedge with warm cherry sauce. Garnish with whipped cream, crème fraîche, or frozen vanilla yogurt, if desired.