Combine beef, sausage, onion, garlic powder, salt, and pepper. Steam 3-5 minutes in covered heavy skillet, until redness disappears from beef. Do not brown. Add mushrooms with juice. Transfer to greased 2 quart baking dish. Cook noodles and drain. Add soup, tomato paste, and tomatoes with juice to noodles. Stir well. Add noodles and half the cheese to meat, mixing well. Sprinkle remainder of cheese over top. Bake at 350 degrees for 30 minutes, or until casserole bubbles and cheese is melted.