In a large bowl, combine the ground beef, finely chopped onion, Parmesan cheese, egg, Italian seasoning, garlic powder, dried parsley, almond flour (or breadcrumbs), salt, and black pepper. Mix until well combined.
Place them on a baking sheet lined with parchment paper. Bake the meatballs for 20-25 minutes, or until they're cooked through and browned on the outside.