For the crust, place the cake mix, melted butter and egg in a large mixing bowl. Blend with mixer on low for 2 minutes. Stop the mixer and scrape down the sides of the bowl with a spatula. With your fingertips, pat the batter evenly over the bottom of the 13 x 9 pan, smoothing it out with your fingers until the top is smooth. Set aside.
For the filling, grate the zest from the lemons and set aside (you should have about 2 tsp.). Cut the lemons in half and squeeze the juice into a small bowl (you should have about 6 tbsp.) Set this aside.
Place the cream cheese in the same mixing bowl that was used to make the crust and with the same beaters (no need to clean either) blend on low speed until fluffy. Add the lemon juice, lemon zest, eggs, melted butter and cornmeal. Beat on medium speed for 1 minute. Add the confectioners sugar and beat until well incorporated, about 1 minute more.
Pour the filling onto the crust and spread with spatula so that the filling covers the entire surface and reaches the sides of the pan. Bake for approximately 45-47 minutes until it is well browned but the center still jiggles. Place on a wire rack to cool, 30 minutes.