Heat 1 tablespoon of olive oil in a large skillet over medium heat. Add 1 pound of lean ground beef and sauté until browned, about 5–7 minutes. Stir in 1 chopped onion, seasoning with salt and pepper, and cook until translucent. Mix in 2 tablespoons of tomato paste and 2 minced garlic cloves, cooking for another minute. Finally, incorporate a can of Ro-tel tomatoes and let it simmer for 5–10 minutes until the mixture thickens slightly.

While the beef mixture simmers, bring a large pot of salted water to a boil. Cook 8 ounces of wide egg noodles according to package instructions until al dente, usually about 8–10 minutes. Drain the noodles well and set them aside.

In a mixing bowl, combine 1 cup of sour cream, 8 ounces of softened cream cheese, and 1 tablespoon of cornstarch. Whisk until the mixture is smooth and creamy.

In a large mixing bowl, carefully stir together the cooked noodles, the beef mixture, and your prepared cheese sauce. Mix until every noodle is thoroughly coated.

Preheat your oven to 350°F (175°C). Transfer the combined mixture into a greased baking dish, spreading it evenly. Top with 2 cups of shredded Colby Jack cheese.

Cover the assembled casserole with aluminum foil and place it in the preheated oven. Bake for 25 minutes. After 25 minutes, remove the foil and bake for an additional 10 minutes, or until the cheese is melted and bubbly.

Once baked, remove the Beef Lombardi Casserole from the oven and let it cool for a few minutes before serving warm.