Preheat the oven to 400 degrees F. Slice the zucchini in half lengthwise. Scoop out the centers to create boats, leaving about ¼ inch of flesh so they hold their shape.
Sprinkle the zucchini with salt and let them sit for 10 minutes to release excess moisture. Pat them dry with paper towels, then lightly season again with salt and pepper. Set aside.
Heat a large skillet over medium heat. Add the ground beef and cook until browned, breaking it up as it cooks.Add the diced onion and cook for 3–4 minutes until softened. Stir in the garlic and cook for 30 seconds until fragrant.
Add the crushed tomatoes, Italian seasoning, sugar, fresh basil, red pepper flakes (if using), salt, and pepper. Stir well. cover, reduce the heat to low, and let the sauce simmer for 15-20 minutes until thickened. Remove from heat.
In a bowl, mix together the ricotta cheese, egg, parmesan cheese, granulated garlic, fresh basil, salt, and pepper until smooth.
Pour a ladle full of the meat sauce in a 9x13 baking dish. Arrange the zucchini boats in the baking dish. Spoon a layer of ricotta filling into each zucchini boat, spreading it evenly.Top with the meat sauce, then sprinkle with mozzarella cheese and parmesan cheese.
Cover loosely with foil and bake for 25–30 minutes, or until the zucchini is tender and the cheese is melted. Remove the foil and bake for an additional 10 minutes, or until the cheese is bubbly and lightly golden. Broil for 1 minute for some extra color.
Serve warm and enjoy!