1 1/2 c. sugar
4 tbsp. cornstarch
3 tbsp. flour
1 1/2 c. water
3 slightly beaten egg yolks
2 tbsp. unsalted butter, cut up
2 tsp. finely grated lemon zest
1/2 c. fresh lemon juice
1 carton Cool Whip
1 large angel food cake

Prepare or purchase 1 large angel food cake. Cover and chill or freeze. In a heavy, medium saucepan, stir together the 1 1/2 cups sugar, the cornstarch and flour; gradually stir in water. Bring to boiling, stirring constantly. Reduce heat; cook and stir over medium heat for 2 minutes. Remove from heat. Gradually stir about 1 cup of the hot mixture into beaten egg yolks; pour yolk mixture back into remaining hot mixture in saucepan. Bring to a gentle boil; cook for 2 minutes more, stirring constantly. Remove from heat; stir in cut up butter and grated lemon peel. Slowly stir in 1/2 cup lemon juice. Pour into glass container; cover and chill several hours or overnight. In a large mixing bowl, combine lemon filling and Cool Whip with an electric mixer on low speed only until combined. DO NOT BEAT or overmix. Frost chilled or frozen angel food cake with lemon mixture. Store covered in refrigerator until serving. If cake is frozen, let it thaw for a short time at room temperature before serving.