Preparation

1. Preheat the oven to 400°F (200°C).
2. Wash zucchini and trim the ends, then slice them in half lengthwise.
3. Scoop out the centers of the zucchini halves to create boats, leaving about 1/4 inch around the edges. Sprinkle a pinch of salt inside each half and let them sit for 10 minutes, then blot with a paper towel.

Cooking the Filling

1. In a skillet, heat a splash of oil over medium heat. Add diced onion and cook for 3 to 4 minutes until softened, then add minced garlic and cook for another 30 seconds.
2. Add the ground beef and break it up, cooking until browned and no longer pink. Drain any excess grease.
3. Stir in Italian seasoning, salt, black pepper, and marinara sauce. Let it simmer for 2 to 3 minutes to thicken.

Assembly and Baking

1. Place the hollowed zucchini in a baking dish, adding a couple of tablespoons of water to the bottom to prevent drying.
2. Fill each zucchini boat with the beef filling and top generously with shredded cheese.
3. Bake in the preheated oven for about 18 to 25 minutes, until zucchini is tender but not collapsing. If desired, broil for 1 to 2 minutes at the end for a bubbly top.

Serving

1. Let the zucchini boats rest for 5 minutes before serving to allow the filling to set.