I found this recipe online, modified it to be gluten free and casein free and it was fantastic!
Ingredients:
1/2 onion, minced
2 tablespoons olive oil
3 cloves garlic, minced
1 pound ground beef
1/4 cup packed chopped Italian parsley
1 egg, beaten
1 1/2 teaspoons kosher salt
1/2 teaspoon freshly ground black

pepper
1 pinch cayenne pepper, or to taste
1/3 cup dry gluten free cracker crumbs
2 tablespoons olive oil
1 (28 ounce) jar marinara sauce
1 cup water
Directions:
1. Saute onion in 2 tablespoons olive oil in a skillet over medium heat until onion is translucent, about 5 minutes. Stir garlic into onion and turn off heat. Transfer onion mixture to a large mixing bowl.
2. Stir ground beef, parsley, egg, kosher salt, black pepper, and cayenne pepper with onion mixture until almost combined; stir in cracker crumbs and continue to mix until thoroughly blended.
3. Roll about 2 tablespoons of mixture into a 1-inch ball for each meatball. Pour 2 tablespoons olive oil in same skillet used to cook onions. Place skillet over medium heat and brown meatballs on all sides in hot oil, about 5 minutes. Hold a crumpled paper towel in a tongs and use it to remove excess grease from skillet.
4. Pour marinara sauce and water over meatballs in skillet. Stir to combine and bring to a simmer. Reduce heat to medium-low and simmer, stirring occasionally, until meatballs are cooked through and no longer pink in the center, about 30 minutes.