Preheat the oven to 400°F (200°C) and line a baking sheet with parchment paper or lightly grease a baking dish.
Add ground beef and ground sausage to a large mixing bowl.
Sprinkle in almond flour, garlic powder, Italian seasoning, salt, and black pepper.
Crack the egg into the bowl and mix the ingredients gently with your hands until evenly combined.
Avoid overmixing the meat mixture so the meatballs stay tender.
Scoop a portion of the mixture and flatten it slightly in your palm.
Place a cube of mozzarella cheese in the center of the meat.
Fold the meat mixture around the cheese and roll it into a sealed ball.
Repeat the process until all meatballs are formed.
Arrange the meatballs evenly on the prepared baking sheet.
Bake for about 20–25 minutes until the meatballs are browned and fully cooked.
Warm the marinara sauce in a saucepan or microwave.
Spoon the marinara sauce over the baked meatballs before serving.
Sprinkle chopped parsley or basil on top for garnish.