1. Preheat the oven to 180°C/350°F/Gas 4. Grease a 19cm/7½in
spring-form cake tin. Line the base with non-stick baking parchment and dust with flour. Beat butter, caster sugar and lemon rind together until pale and fluffy. Gradually whisk in the eggs.
Fold in alternate spoonfuls of flour and ground almonds, then stir in the liqueur or almond essence. Spread into the tin and level. Bake for 40 minutes or until a skewer inserted into the centre comes out clean. Leave to settle in
the tin for 5 minutes, then turn out to cool on a wire rack.
3. For the decoration, skin the whole almonds by immersing them in boiling water for 1 minute. Plunge them into cold water
and and their skins will rub off. Slice th almonds thinly and heat gently in a non-stick frying pan for 1-2 minutes, or until golden. Dust the top of the cake with icing sugar, mark into slices, then scatter the toasted almonds over.