Preheat the oven to 180C/375F/Gas 4. Lightly grease and line the base of a 25cm/10in springform tin with a little oil.
Place the apples in a pan with half the lemon juice and two tablespoons of the caster sugar. Simmer, cover and cook on a low heat for about 7-9 minutes or until the apples are soft enough to roughly mash with a fork. Do not over-mash, though. You still want a little bite and texture. Leave to cool.
Put the cooled apple, eggs, ground almonds, almond essence, remaining caster sugar and approximately one tablespoon of the remaining lemon juice into a food processor and blend together.
Pour into the prepared cake tin and sprinkle with the flaked almonds.
Bake for about 40 minutes or until a skewer inserted into the cake comes out clean.
Check the cake after about 30 minutes, and if the cake is getting too brown cover the top with parchment paper or foil.
Leave to cool slightly before you remove the cake from the tin.