Makes 1 x 25.5cm/10 in cake.

1. Preheat oven to 150C/300F/Gas 2. Butter a 25.5cm/10in round cake tin and line with greaseproof paper.

2. Coarsely chop the almonds in a food processor. Combine with the flour and lemon zest.

3. Beat the butter and sugar together in a mixer until pale and light. Add the egg yolks one by one, then add the almond mixture.

4. Put the ricotta in a bowl and lightly beat with a fork. Add the lemon juice. In another bowl, beat the egg whites until they form soft peaks. Fold the egg whites into the almond mixture and finally stir in the ricotta.

5. Spoon the mixture into the prepared tin and bake in the preheated oven for 35-40 minutes until set. Test by inserting a skewer, which should come out clean. Remove from tin while warm, and cool on a rack.