In a large skillet, heat olive oil over medium heat. Add lean ground beef and chopped onion, browning until the beef is no longer pink, about 5-7 minutes. Drain excess fat and season with salt, pepper, tomato paste, and minced garlic. Cook for an additional 2-3 minutes until fragrant.

While the beef is cooking, bring a large pot of salted water to a boil and cook wide egg noodles until al dente, about 7-9 minutes. Drain noodles and set aside to cool slightly.

In a mixing bowl, whisk together sour cream, softened cream cheese, and cornstarch until smooth and well combined.

In a large mixing bowl, combine drained egg noodles, cooked beef mixture, and cheese sauce. Gently fold together until evenly coated.

Preheat oven to 350°F (175°C). Grease a 9x13 inch baking dish and layer half of the noodle mixture in the bottom. Sprinkle half of the shredded Colby jack cheese on top. Repeat layering with remaining noodle mixture and cheese.

Bake uncovered for 25-30 minutes until cheese is melted and bubbly.

Let cool for a few minutes before serving.