Baked Ziti with Spinach and Ricotta (no meat)

Ingredients

• 1 lb ziti or penne pasta
• 1 tbsp olive oil
• 1 medium onion, chopped
• 1 zucchini, small diced
• 1 red bell pepper, cored and diced
• 3 garlic cloves, minced
• 1 tsp kosher salt
• 1 tsp dry oregano
• 1/2 tsp red pepper flakes (optional)
• 3 cups marinara sauce
• 3 cups spinach
• 1 cup ricotta
• 1/4 cup grated parmesan
• 4 oz shredded mozzarella
• fresh basil, for topping