In a large bowl, combine ground beef, ground pork, Parmesan, almond flour, egg, garlic, Italian seasoning, onion powder, salt, pepper, and red pepper flakes. Mix just until combined — don't overwork the meat.
Divide the mixture into 16 equal portions. Press each portion flat, place a mozzarella cube in the center, and seal the meat around it, rolling into a smooth ball.
Heat a 12-inch cast iron skillet over medium-high heat and add olive oil.
Sear meatballs in batches, turning every 2-3 minutes, until browned on all sides — about 8 minutes total. Remove and set aside.
In the same skillet, reduce heat to medium. Add olive oil and garlic for the sauce, cooking 1 minute until fragrant.
Pour in crushed tomatoes. Add basil, oregano, salt, pepper, and red pepper flakes. Stir to combine.
Nestle meatballs back into the sauce. Simmer on low, partially covered, for 15 minutes until cooked through (internal temp 165°F).