Preheat your oven to 350°F (175°C).
In a skillet over medium heat, brown the ground beef with chopped onion until fully cooked. Drain excess fat.
Meanwhile, cook the egg noodles according to package directions. Drain and set aside.
In a large mixing bowl, combine the tomato soup, cream of mushroom soup, and milk. Stir until smooth.
Add the cooked beef and noodles to the soup mixture. Stir well to combine.
Season with salt and pepper to taste.
Transfer the mixture into a greased 9x13-inch baking dish.
Bake uncovered for 30 minutes or until heated through and slightly bubbly.
Optional: Garnish with chopped parsley before serving.