1. Preheat the oven to 180°C/gas 4. Grease a 23cm cake tin and line with greaseproof paper. Brush the paper with oil.

2. Cream the butter, sugar and salt in a food processor until light and fluffy.

3. Mix in the lemon zest and crème fraîche.

4. Gradually mix in the eggs and flour, then the ground almonds.

5. Spoon the mixture into the prepared cake tin, levelling the top with a palette knife.

6. Bake for 20-25 minutes until the cake is trembling.

7. While the cake is baking, whisk the egg whites for the macaroon mixture. Whisk in the caster sugar, then fold in the ground almonds.

8. Remove the cake from the oven. Spread the macaroon mixture over the top.

9. Bake for a further 20 minutes at the same temperature, until the topping is set.