Steps

• Start by heating a large skillet over medium heat. Add sliced onions and cook until they start to caramelize, which takes about 10-15 minutes. Stir occasionally to prevent burning. Once the onions are golden and soft, add the ground beef. Cook until the beef is browned, breaking it apart with a wooden spoon. This usually takes another 5-7 minutes. Once cooked, drain any excess fat from the skillet.
• After draining the fat, return the beef and onion mixture to the skillet. Stir in the onion soup mix, beef broth, and sour cream. Mix thoroughly until well combined, ensuring the flavors meld together beautifully. Let the mixture simmer for about 5 minutes, allowing it to thicken slightly. Taste and adjust seasoning with salt and pepper as needed.
• Preheat your oven to 350°F (175°C). Transfer the beef mixture into a large mixing bowl and fold in the pasta if you're not going low-carb. Pour this mixture into a 9x13-inch baking dish. Spread it out evenly using a spoon, ensuring the entire surface is covered.
• Generously sprinkle the shredded mozzarella cheese over the beef mixture. Place the baking dish in the preheated oven and bake for about 20 minutes or until the cheese is melted and bubbly with a golden brown hue. Let it sit for a few minutes to set before serving.