Preheat your oven to 350°F (175°C).

Cook the egg noodles in a large pot of boiling salted water until al dente. Drain and set aside. Tip: Be sure not to overcook the noodles, as they will continue to cook in the oven.

In a large skillet over medium heat, brown the ground beef. Season with garlic salt. Drain excess fat, if necessary. Stir in the marinara sauce and let it simmer for 10 minutes. Tip: Adding a pinch of red pepper flakes can give an extra kick to the sauce.

In a medium bowl, mix together the sour cream, cream cheese, and chopped onion until well combined. Tip: For added flavor, consider mixing in some herbs like parsley or basil into the sour cream mixture.

In a 9x13-inch baking dish, layer half of the cooked noodles, followed by the meat mixture, then the sour cream mixture, and finally the remaining noodles.

Top the casserole with grated Cheddar cheese and bake for 25 minutes. Tip: For a golden crust, broil the casserole for an additional 2-3 minutes at the end.

Once done, serve and enjoy your delicious Cheesy Beef Noodle Casserole!