Mix together the courgette, lemon rind, spring onions, herbs, feta, rice flour and egg yolk in a large bowl and season well. Gently stir in the beetroot until the mixture is just speckled with red.
Heat a little of the oil in a frying pan, add tablespoons of the mixture to the pan and fry the fritters for 1–2 minutes on each side until golden. Transfer to a serving plate and keep warm while frying the remainder of the mixture, adding the remaining oil to the pan as necessary.
Garnish the fritters with basil leaves and a mixed leaf salad.