Prepare the Beef Filling: In a large pan over medium heat, cook the finely chopped onion until softened. Add the minced beef, breaking it up as it cooks. Season with salt, black pepper, and sweet paprika to taste. Cook until the beef is browned and fully cooked through. Let it cool for a few minutes before mixing in the beaten eggs. This will help bind the mixture together for filling the pasta tubes.
Stuff the Cannelloni: Using a spoon, carefully stuff each cannelloni tube with the prepared beef filling. Be generous with the filling to ensure each tube is packed tightly. Place the stuffed cannelloni in a greased baking dish.
Assemble the Dish: Pour the tomato sauce evenly over the stuffed cannelloni. Sprinkle the shredded mozzarella cheese over the top, ensuring it covers the entire dish. If desired, add a bit of grated Parmesan cheese for extra flavor.
Bake the Cannelloni: Preheat the oven to 375°F (190°C). Cover the baking dish with aluminum foil and bake for 30 minutes. After 30 minutes, remove the foil and continue to bake for an additional 10 minutes or until the cheese is golden and bubbling.
Serve and Enjoy: Once baked, remove the cannelloni from the oven and let it rest for a few minutes. Serve with a side salad or some crusty bread, and enjoy the delicious flavors of homemade Italian cuisine.