In a large saucepan or deep skillet, heat the olive oil over medium-high heat.
Add the beef loin to the sausage and cook for 5-7 minutes until browned.
Remove the casing from the Italian sausage and add it to the pan. Break the sausage into smaller pieces with a wooden spoon as it cooks. Cook until browned and cooked through, about 5-7 minutes.
Add the chopped onion and sauté for 5 minutes, or until translucent.
Stir in the minced garlic. Cook for 1 minute until fragrant.
Pour in the tomato sauce, sugar, Italian seasoning, and salt and pepper to taste. Stir well to combine.
Reduce the heat to low and simmer the sauce, covered, for at least 20-30 minutes. Simmer it for longer to enhance the flavor.
Add the cooked meatballs allow them to heat through.
Taste the sauce and adjust the seasoning, sugar, or spices according to your preference.