Caramelized Onion, Red Pepper and Zucchini Frittata

Bahan-bahan (4 porsi)

• 1 white onion (thinly sliced)
• 1 medium red bell pepper (diced)
• 1 1/2 cups zucchini (diced into matchsticks)
• 6 large eggs
• 1/4 cup Parmesan cheese (grated)
• 2 tsp olive oil
• salt and fresh pepper (to taste)