1. Preheat your oven to 375°F. Rinse the zucchini thoroughly, trim the ends, slice each zucchini in half lengthwise, and scoop out the center flesh, leaving about a 1/4-inch border.

2. Arrange the hollowed-out zucchini halves on a large baking sheet. Drizzle lightly with olive oil and season with salt and pepper. Bake for 10 minutes.

3. Heat 1 tablespoon of olive oil in a large skillet over medium-high heat. Add the diced onion and sauté for about 3 to 4 minutes until tender. Add the ground beef, breaking it apart as it cooks for about 5 to 6 minutes until browned. Drain excess fat.

4. Stir in minced garlic, tomato paste, Italian seasoning, garlic powder, smoked paprika, salt, black pepper, and optional red pepper flakes. Cook for a minute until fragrant. Add chopped zucchini flesh and tomato sauce, stirring to combine. Let simmer for 5 to 8 minutes.

5. Remove zucchini from the oven and spoon the ground beef filling into each boat. Sprinkle shredded mozzarella cheese over each filled zucchini boat and dust with freshly grated Parmesan cheese.

6. Return the baking sheet to the oven and bake for an additional 20 to 25 minutes until cheese is melted and bubbly, and zucchini is fork-tender.

7. Let cool for about five minutes before serving. Garnish with freshly chopped parsley or basil.