Ricotta Filled Cake

1 box yellow cake mix
2 15-oz. containers ricotta cheese
2 eggs, beaten
4 egg whites, beaten
½ c. sugar
½ t. vanilla

Mix your cake according to box directions, pour batter into a greased 13 x 9-inch baking dish. 
Combine the cheese, eggs, egg whites, sugar and vanilla and mix well. 
Pour mixture over cake batter and bake for about an hour at 300 degrees.