Make the marinara meat sauce that will go inside the zucchini boats by browning the ground beef. Add the onion, Italian seasoning, salt, pepper, and marinara sauce.
Take the zucchini, cut in half lengthwise and scoop out the seeds. Pat the inside dry with a paper towel. Lightly mist with oil and sprinkle with salt.
Place the zucchini in the air fryer basket and cook at 380°F/190°C for 8-10 minutes until cooked through. The cooking time will depend greatly on the size of your zucchini and how cooked through you want it to be. Check on the zucchini after 5 minutes and adjust as needed. Once your zucchini reaches its desired tenderness, pat dry any excess moisture from the zucchini, add the marinara meat sauce, sprinkle on parmesan cheese, and cook for an additional 2-3 minutes, or until cheese is melted.
Carefully remove from the air fryer basket and enjoy!