Ricotta apple streusel bars

It's a quite delicious bars. I'm sure, you will make this recipe over and over again.

2 cups flour, 3/4 cup butter or margarine, 3/4 cup sugar, 1 teaspoon baking powder
250 gramm ricotta cheese, 100 gramm sourcream, 2 large eggs, 2 large sheredded apples, 1/2 cup sugar, vanilla extract

Make a streusel. In a medium bowl, combine flour, sugar, and baking powder. Using a pastry blender or fork, cut in the butter until fine crumbs form. Remove 1/3 cup flour mixture; place in a small bowl.

In a separate bowl mix together ricotta, sourcream, sugar, vanilla extract, eggs and shredded apples.

Press rest of the dough evenly over the bottom of a buttered 9- by 9-inch baking pan. Spread ricotta-apple mixture evenly over dough. Crumble remaining dough evenly over ricotta mixture; pat lightly.
Bake in a 350F° oven until streusel is lightly browned, 45 to 50 minutes. Place pan on a rack to cool for about 10 minutes. While still warm, cut into bars. Let cool completely in pan.