In large skillet, cook beef and onion until beef is thoroughly cooked; drain well. Stir in pasta sauce; cook until heated through.
Combine mozzarella cheese and sour cream.
Pour hot beef mixture into ungreased 10-inch (25 cm) glass deep dish pie plate or 9x13-inch (23 x 33 cm) rectangular baking pan. Spoon cheese mixture over beef mixture.
Separate dough into 4 rectangles and place over cheese mixture. (If using pie plate, separate dough into 8 triangles: arrange points toward center over cheese mixture.)
Combine Parmesan cheese and butter. Spread evenly over dough.
Bake for 18 to 25 minutes or until deep golden brown.