Preheat the oven to 350°F (175°C).
Cook the egg noodles according to package instructions until al dente. Drain and set aside.
Heat olive oil in a large skillet over medium heat. Add diced onion and cook for 3-4 minutes until softened.
Add minced garlic and cook for 30 seconds until fragrant.
Add ground beef to the skillet and cook, breaking it up with a spoon, until browned and cooked through, about 6-8 minutes. Drain excess fat.
Stir in tomato sauce, diced tomatoes with juice, dried Italian seasoning, salt, and black pepper. Simmer for 5 minutes, stirring occasionally.
Remove the skillet from heat and stir in sour cream until well combined.
In a large mixing bowl, combine the cooked egg noodles and the beef mixture. Mix gently to combine.
Transfer half of the noodle and beef mixture into a 9×13-inch baking dish. Sprinkle half of the cheddar and mozzarella cheese evenly over the layer.
Add the remaining noodle and beef mixture on top and spread evenly.
Sprinkle the remaining cheddar and mozzarella cheese over the casserole.
Bake in the preheated oven for 25-30 minutes, until the cheese is melted and bubbly.
Remove from the oven and let it cool for 5 minutes before serving.