Preheat your oven to 350°F and lightly grease a 9x13-inch baking dish.

Dice the onion and add it to a skillet along with the minced garlic. Cook over medium heat, stirring occasionally, until softened, about 5 minutes.

While the onion and garlic are cooking, bring a pot of water to a boil and cook the egg noodles according to the package directions.

Add the ground beef to the skillet. Cook, breaking it up with a spoon, until browned and mostly cooked through with no pink remaining.

Stir in the diced tomatoes, tomato sauce, oregano, salt, and pepper. Let everything simmer for a few minutes so the flavors come together.

Drain the cooked noodles well, then add them directly to the skillet. Gently toss until the noodles are fully coated with the sauce and beef mixture.

Transfer the mixture to the prepared casserole dish. Sprinkle the cheese evenly over the top and bake uncovered for about 20 minutes, or until the cheese is melted and bubbly.

Remove from the oven, garnish with fresh parsley, and serve warm.