In large bowl, thoroughly combine ground beef, chopped onion, fresh herbs, garlic, egg, almond flour, salt, and pepper.
Use cookie scoop or tablespoon to portion out ground beef mixture into meatballs, each containing 2 tablespoons of mixture. Quickly roll meatball between palms to round out, then place on plate or baking sheet. Continue until all ground beef mixture has been portioned.
Heat neutral oil in large skillet over medium-high heat. Once oil is hot and shimmering, add meatballs, being careful not to overcrowd skillet. Cook 3 to 5 minutes, turning frequently, until meatballs are browned on all sides. Transfer to plate or bowl and repeat until all meatballs have been cooked.
Once all meatballs are browned, return all to skillet and add marinara sauce. Stir well to coat meatballs, then bring to simmer over medium heat and cook 5 to 8 minutes, until sauce is hot and meatballs are cooked through.
Divide meatballs and sauce into equal portions and serve with fresh basil and zucchini noodles, if desired.