Combine eggs together with sugar; whisk mixture until it's light and airy.
Using a spatula, in small portions, fold in flour to the egg mixture. Use the folding motion to keep the mixture airy. Grease a 9x13 baking sheet and pour the cake batter into the baking sheet.
Bake the sponge cake at 350F for 30 minutes. Once the cake is ready, the toothpick should come out clean from the cake. Let the sponge cake cool to a room temperature and poke holes in it. Prepare the jello according to the package instructions.
Once the jello fully cools to the room temperature, pour the jello mixture over the sponge cake. Cover the top of the cake with Cool Whip.
Let the cake rest for at least a few hours before serving.