Aunt Polly's Sponge Cake

6 separated eggs
1.5 cups sugar
1.5 cups flour (measured after sifting)
1 tsp cream of tartar
6 Tbsp hot water
1 dash salt

Beat egg yolks well, put in 1/2 of sugar and beat well again. Add hot water and flour. Beat egg whites until stiff, add cream of tartar, salt and rest of sugar. Fold egg white mixture into egg yolk mixture. Bake in an ungreased angel food pan at 375 degrees for about 45 minutes or until done.