Found this recipe and a picture at: http://allrecipes.com/Recipe/Mock-Angel-Food-Cake/Detail.aspx
Mock Angel Food Cake
SUBMITTED BY: Melissa Busse
"This is an angel food cake for a sheet cake. My grandma used to use this when she had a bakery. I have never had a problem with it. It is so easy to do."
4 1/2 cups cake flour
4 cups white sugar
2 teaspoons salt
2 cups boiling water
16 egg whites
2 tablespoons baking powder
2 teaspoons cream of tartar
2 teaspoons vanilla extract
1 teaspoon almond extract
Preheat oven to 350 degrees F (175 degrees C).
Sift cake flour, sugar, and salt three times then stir in the boiling water. Let cool.
Beat egg whites, cream of tartar, baking powder, vanilla and almond flavorings until stiff peaks form. Fold into the flour mixture and pour batter into one ungreased 12x18 inch baking pan.
Bake at 350 degrees F (175 degrees C) for 35 minutes. Cool cake inverted in pan, laying a tea towel underneath the cake to absorb the steam. Frost as desired once the cake is cooled.