Preheat oven to 350.
In a large skillet, over medium heat, brown the ground beef (or bulk sausage or combination of both) until the meat is no longer pink.
Drain off the fat and transfer the cooked meat to a clean plate or bowl.
Finely chop an onion.
Sauté the onion in a few tablespoons of meat drippings until soft, translucent and slightly golden on some of the edges.
Cook pasta about a minute short of al dente.
In a large bowl, combine the ground beef and sautéed onions.
Combine the tomato paste, pizza sauce and tomato sauces and add to the beef and onion mixture.
Stir to combine.
Add the cooked noodles to the bowl and stir to combine Be sure to get all the noodles up from the bottom and coated with the sauce/meat/onion mixture.
Spray a 9 x 13 baking dish with non stick spray for easier clean up.
Spoon half the noodle/meat mixture into the 9x13 casserole dish.
Spread half of the mozzarella cheese over the noodles.
Place the pepperoni in a single layer over the noodles. (Feel free to add other pizza toppings at this point. Green bell pepper, mushrooms, and ricotta cheese, just to name a few.)
Repeat the process of adding the second half of the pasta/meat mixture and mozzarella cheese.
Add one more layer of pepperoni.
Bake at 350 for 45 minutes or until heated through and cheese is melted and bubbly.
Serve warm and gooey.