For the cake: – 1 (15.25 oz.) pkg. white cake mix – 3 egg whites – 1/2 cup vegetable oil – 1 cup water Poke cake filling and topping: – 1 (3 oz.) pkg., Lemon flavored Jell-o mix – 1 cup boiling water – 1/2 cup cold water – 1 (3 oz.) pkg., Lemon pudding mix – 1 1/2 cup cold milk – 1 (8 oz.) carton, Cool Whip whipped topping, thawed
Preheat oven to 350 degrees. Lightly spray a 9 x 13" pan with non-stick spray. Set aside.
Remove the cake from the oven and let cool for 15-20 minutes. Using a straw or the end of a wooden spoon, poke holes 1" apart into the baked cake.
Prepare the lemon Jell-o by adding the mix to the boiling water. Stir well to dissolve the mix. Add the cold water and stir. Pour the lemon Jell-o liquid into the holes of the cake, making sure all of the holes are filled. Refrigerate the Jell-o cake for at least 1 hour.
Once chilled, prepare the lemon pudding mix, by mixing the cold milk with the lemon pudding mix. Once slightly thickened, pour over the top of the chilled cake, lightly pressing the pudding into the holes.
Top the pudding layer with the Cool Whip, evenly covering the top of the cake. Chill for another 30 minutes.
Chill the cake in the refrigerator until ready to serve. Cut into 20 squares. Serve with fresh berries and/or lemon slices.