- Heat 1/2 Tbsp oil in a 10-inch, heavy-bottomed, oven-proof skillet.
- Add onion and sauté until tender and translucent.
- Stir in garlic and zucchini and continue sautéing until squash is just tender.
- Season with salt and pepper and remove from heat.
- In a mixing bowl, whisk together eggs, basil and parsley.
- Stir in sautéed vegetables.
- Add remaining 1/2 tablespoon oil to same skillet over medium heat, tilting pan to coat bottom and sides.
- Add egg-vegetable mixture, spreading evenly.
- Reduce heat to low and cover pan.
- Cook 10 to 15 minutes, until set.
- Preheat broiler.
- Sprinkle grated cheese on top of frittata if desired and broil briefly until lightly browned.
- Cut into 3 wedges.
- Serve immediately from the pan or transfer to a large round plate or platter.