Cook the spinach and noodles separately and set aside. Brown meats and onion in oil. Add tomato sauce, salt and oregano. cover, simmer 30 minutes. Mix in spinach. Spoon half noodles into baking dish. Top with half meat mixture and Parmesan cheese. Top with layers or remaining noodles, meat and Parmesan. Spread with sour cream. Sprinkle with Monterey Jack and onion. Microwave at half intensity 10 minutes or in regular oven 30 minutes at 300ºF. Serves 8.