1Heat oven to 350°F (325°F for dark or nonstick pans). Grease and lightly flour bottoms only of two 8-inch or 9-inch round pans, or spray with baking spray with flour.
2Make and cool cake as directed on box, using whole eggs and adding lemon peel with the water and oil.
3Place 1 cake layer, rounded side down, on serving plate. Spread 2/3 cup pie filling over layer. Top with second layer, rounded side up. Frost side with frosting, building up a slight edge at top of cake. Spread 2/3 cup pie filling over top of cake to frosted edge. Store loosely covered in refrigerator.