Preheat your oven to 400°F.
In a large mixing bowl, combine the ground beef, ground turkey, grated onion, breadcrumbs, salt, and pepper. Add the egg and mix thoroughly until all ingredients are well combined. Using a tablespoon, portion out the mixture and roll into meatballs.
In a large, oven-safe skillet, heat the olive oil over medium heat. Add the minced garlic and sauté for about a minute until fragrant.
Next, pour in the passata and chicken broth. Stir in the sugar, salt, and pepper, then let the mixture simmer for 2-3 minutes.
Carefully place the meatballs into the sauce, ensuring they are evenly distributed. Using a spoon, drizzle some sauce over each meatball to keep them moist while baking.
Top with a generous amount of grated cheese. Bake in the preheated oven for 18-20 minutes, or until the cheese is golden and the meatballs are cooked through.
Enjoy your meal with your favorite sides!