Preheat the oven to 200°C (400°F), Gas Mark 6. Place the chickpeas, cumin and coriander in a food processor or blender and pulse until the chickpeas resemble coarse breadcrumbs. Scrape into a large bowl and add the onion, finely grated carrot, garlic, parsley, egg, lemon rind, flour, baking powder and chilli flakes and mix until well combined.
Lightly grease a nonstick baking sheet and form walnut-sized spoonfuls of the mixture into 24 slightly flattened patties and place on the baking sheet. Put the falafel in the oven and for 12–15 minutes until golden and crisp.
Arrange the patties inside warmed wholemeal pittas and serve with the grated carrots and low-fat tzatziki.