3 tablespoons caster sugar, plus extra for sprinkling
knob of unsalted butter, for frying
Place the ricotta, milk, egg yolks and lemon rind in a large bowl and beat together. Stir in the flour, baking powder, salt and sugar.
Whisk the egg whites in a clean large bowl with a hand- held electric whisk until stiff, then gently fold into the ricotta mixture.
Heat a little of the butter in a large frying pan over a medium heat and add heaped dessertspoons of batter to form pancakes about 7 cm (3 inches) in diameter. Cook for 1–2 minutes on each side until golden brown. Remove from the pan and keep warm. Repeat with the remaining batter to make about 24 pancakes, adding a little more butter and reducing the heat if necessary.
Serve a small stack of pancakes on each of 4 plates, drizzled with the lemon juice and sprinkled with a little caster sugar.