Preheat the oven to 375°F (190°C).
In a large mixing bowl, combine the ground beef, ground pork, mozzarella cheese, grated Parmesan cheese, egg, almond flour, garlic powder, onion powder, Italian seasoning, salt, and black pepper. Mix until well combined.
Form the mixture into meatballs, roughly 1 inch in diameter, and place them on a baking sheet.
Bake the meatballs in the preheated oven for about 25 minutes or until cooked through and browned.
While the meatballs are baking, heat the marinara sauce in a skillet over medium heat until warmed through.
Once the meatballs are done, remove them from the oven and add them to the skillet with the marinara sauce. Stir gently to coat the meatballs in the sauce.
Transfer the meatball and sauce mixture to a baking dish, spreading it evenly.
Sprinkle the shredded cheddar cheese on top of the meatball mixture.
Return the baking dish to the oven and bake for an additional 15-20 minutes, or until the cheese is bubbling and golden.
Remove from the oven and let it sit for a few minutes before serving. Garnish with fresh basil if desired.