Taco Stuffed Pasta Shells

18 jumbo pasta shells, cooked & tossed with butter
1 1/4 lb. ground chuck
8-oz. cream cheese
1 tsp. salt
1 tsp. cayenne pepper
16-oz. taco sauce
4 oz. shredded Cheddar cheese
4 oz. shredded Monterey Jack cheese
1 cup sour cream
Green onions

Cook beef in large skillet over medium heat; drain. Reduce heat; add cream cheese, salt and cayenne pepper. Simmer 5 minutes. Stir. Fill shells with meat mixture and arrange in buttered 9x13 pan. Pour taco sauce over each shell. Cover with foil and bake for 15 minutes at 350. Uncover, top with cheeses, and bake uncovered 15 more minutes. Top with green onions and sour cream.