Sour Cream Coffee Cake III

Preheat oven to 350 degrees F (175 degrees C). Grease a 9x13 inch baking pan. In a large bowl, cream together 1 cup butter and white sugar until light and fluffy. Beat in the eggs one at a time, then stir in the sour cream and vanilla. Mix in 2 cups flour, baking powder, and salt. Spread 1/2 of batter in the prepared pan. Prepare the filling: In a medium bowl mix 1/3 cup flour, brown sugar, 2 tablespoons melted butter, and cinnamon. Sprinkle cake batter with 1/2 the filling. Spread second half of batter over the filling, and top with remaining filling. Bake 35 to 40 minutes in the preheated oven, or until a toothpick inserted near the center comes out clean.