Baked Zucchini ‘Ziti’ Spirals with Mozzarella

Ingredients

• 5 zucchini, ends trimmed
• 1 tablespoon extra-virgin olive oil
• ½ sweet onion, minced
• 2 garlic cloves, minced
• 1½ cups ricotta cheese
• 1 cup grated mozzarella cheese
• 1 teaspoon dried oregano
• ¼ teaspoon red pepper flakes, or more to taste
• Salt and freshly ground black pepper
• 2 cups marinara sauce
• ⅓ cup grated Parmesan cheese
• Basil, as needed for finishing