Preheat your oven to 375°F (190°C).
In a large mixing bowl, combine the ground beef, ground pork, almond flour, egg, minced garlic, onion powder, Italian seasoning, salt, and black pepper. Mix well until all ingredients are fully incorporated.
Form the mixture into meatballs about 1 inch in diameter and place them on a baking sheet.
In a medium skillet, heat a small amount of oil over medium heat. Brown the meatballs for about 5-7 minutes, turning occasionally to sear all sides.
In the baking dish, spread half of the marinara sauce on the bottom. Arrange the browned meatballs in a single layer on top.
Pour the remaining marinara sauce over the meatballs, ensuring they are fully covered.
Sprinkle the shredded mozzarella and grated Parmesan cheese evenly over the top of the casserole.
Bake in the preheated oven for 25-30 minutes or until the meatballs are cooked through and the cheese is bubbly and golden.
Remove from the oven and let it cool for a few minutes before serving. Garnish with fresh basil if desired.