Preheat the oven to 190°C/Fan 170°C/Gas Mark 5. Lightly oil a 20cm (8in) nonstick baking tin. Heat the oil in a nonstick frying pan, add the butternut squash and peppers and sauté for 8 mins or until almost tender and golden. Transfer to the tin and stir in the chickpeas and rocket leaves.
Now beat the eggs with the cumin, chilli flakes and plenty of seasoning. Pour into the baking tin over the vegetables. Place on a baking sheet and bake for 20-25 mins or until the frittata is set in the middle and the top golden.
Leave to cool for 5 mins, before turning out and cutting into squares. Serve warm or cold with a crisp salad. If you like, mix a handful of chopped coriander with the sour cream.