Preheat oven to 350. Lightly grease 13 x 9 pan.

Measure out 1/2 cup cake mix and reserve.

Place remaining cake mix and 1 egg and melted butter in large mixing bowl. Blend at low speed for 2 minutes. With your finger pat dough on bottom of pan.

For your filling, place cream cheese and sweetened condense milk in same mixing bowl that was used for crust. Mix for 30 seconds. Stop the machine and add reserve cake mix, 3 remaining eggs, the sour cream, Lemon juice, and vanilla. Beat for 1 minute. Pour onto crust.

Bake until it looks shiny and the center no longer juggles. About 35 to 40 minutes.Remove the pan from oven while you prepare the topping.

Mix 1 cup sour cream with 1/2 cup sugar. Spread on top of cake. Bake 7 to 10 minutes.

Allow to cool and place in refrigerator covered preferably over night or 24 hours