Preheat the oven: Heat to 400°F (205°C). Line a rimmed baking sheet with parchment paper and lightly oil it. You can also use an air fryer at 375°F (190°C).
Mix the base: In a large bowl, add the sausage, ground beef, cheddar, Parmesan, almond flour, eggs, garlic, onion powder, Italian seasoning, red pepper flakes, salt, pepper, and parsley.
Combine gently: Use your hands to mix until just combined. Do not overmix; that can make the meatballs tough.
Form meatballs: Scoop about 2 tablespoons per meatball (roughly golf-ball size).
Roll lightly and place on the prepared sheet, leaving space between each.
Optional test patty: If you’re worried about salt, cook a small piece in a skillet, taste, and adjust seasoning.
Bake: Place in the oven for 16–20 minutes, until browned and the internal temperature reaches 160°F (71°C). If you want extra color, broil for 1–2 minutes at the end.
Air fryer option: Air fry in a single layer for 10–12 minutes at 375°F (190°C), shaking or turning once, until cooked through.
Rest and serve: Let the meatballs rest 5 minutes. Serve with a warm spoonful of low-sugar marinara, pesto, or garlic butter, and garnish with extra parsley if you like.