Boil the potatoes for 10 minutes, until tender, then drain and slice thickly.
Meanwhile, heat 1 tablespoon of oil in a 23cm frying pan over a medium heat. Add the onion and cook for 5-10 minutes, until soft, adding the garlic for the last minute.
In a large bowl, lightly whisk the eggs with half the cheese. Add the onion, garlic, potato and spinach, and stir gently to coated all the vegetables.
Heat the remaining 1 tablespoon oil in the frying pan. Pour in the frittata mixture and top with the tomatoes. Sprinkle over the remaining cheese and cook over a low heat for 12 minutes, until the bottom has set.
Meanwhile, boil the broccoli and courgettes for 3-4 minutes, then drain. Preheat the grill to hot.
Place the frittata pan under the grill for 5 minutes, until the egg is cooked through. Cut into 4 and serve with the broccoli and courgettes.