Preheat the oven to 400 degrees.
Cut off the ends of the zucchini and slice them in half lengthwise. Use a spoon to scoop out the middle part of the zucchini and throw it away.
Place the hollow zucchini on a baking sheet with parchment paper and set it aside.
Cook the ground beef in a pan over medium heat until it's no longer pink, about 5-7 minutes. Drain the fat, remove the meat from the pan, and set it aside.
In the same pan, cook the onion for 4 minutes until soft. Then add the garlic and cook for 1 more minute.
Add the beef back to the pan with Italian seasoning, salt, pepper, and marinara sauce. Mix everything well and cook for 5 minutes.
Spoon the meat mixture evenly into the zucchini halves. Bake them for 20 minutes.
After 20 minutes, sprinkle cheese on top of the zucchini and bake for another 3-5 minutes until the cheese melts.
Sprinkle parsley on top and enjoy!