In a large skillet, cook the ground beef and chopped onion over medium heat until the beef is browned and the onion is tender. Drain off any excess grease.
Stir in the cream of mushroom soup, evaporated milk, diced tomatoes (undrained), salt, and pepper. Bring to a simmer.
Add the cooked egg noodles to the skillet and stir to combine.
Pour the mixture into a 9x13 inch baking dish.
Sprinkle the shredded cheddar cheese evenly over the top.
Bake for 20-25 minutes, or until heated through and the cheese is melted and bubbly.