Preheat oven to 350°.

Filling:

In a small bowl, beat cream cheese or ricotta until smooth. 

Add egg yolks, sugar and vanilla. Mix thoroughly and set aside.

Batter:

In a separate bowl, cream butter and sugar.

Add eggs and beat well.

In a third bowl, mix flour and baking powder.

Add flour to egg mixture alternately with yogurt and orange juice. Stir only until moistened.

Assembling:

Pour half the batter into a buttered 9 x 13-inch baking dish.

Spread filling over batter. Filling will be thick. Cover with remaining batter.

Bake in preheated oven for 50 minutes. Let cool down before cutting.

Serve with warmed fruit sauce and sour cream or yogurt.