Pepperoni Cheese Ravioli

1 (25 ounce) package frozen cheese ravioli
1/2 pound fresh mushrooms, sliced
1 (3 1/2 ounce) package sliced pepperoni, diced
1 small onion, cut into wedges
1 tablespoon butter or margarine
1 (8 ounce) can tomato sauce
1/4 cup grated Parmesan cheese
1/2 teaspoon garlic powder
1/2 teaspoon dried basil
1/2 teaspoon dried oregano
1/8 teaspoon cayenne pepper
1/2 cup sour cream

Cook ravioli according to package directions.

Meanwhile, in a large saucepan, saute mushrooms, pepperoni and onion in butter until onion is tender. Stir in tomato sauce, Parmesan cheese, garlic powder, basil, oregano and cayenne; heat through. Remove from the heat; stir in sour cream. Drain ravioli; toss with cream sauce.