Preheat oven to 425. Brown hamburger meat and drain. Add spaghetti sauce, tomato paste, onion, bell pepper, mushrooms, black pepper, and water. (Pour water into spaghetti sauce jar and shake to get all of the sauce out of the jar.) Cover pot and simmer for 15 minutes. Using a lasagna pan, begin making layers. Place a layer of noodles on the bottom, then cover with sauce mix and cheese. Continue layering, finishing with a big layer of cheese on top. (You may need more than 8 cups!) Put baking pan on a cookie sheet, to catch any spills, cover pan tightly with foil and bake for 45 minutes. Uncover and bake another 15 minutes until cheese is bubbly. Let stand 10 minutes before serving.