Pre heat oven to 180°C/350°F/Gas Mark 4
Beat butter and sugar together until it looks light and fluffy.
Beat in eggs gradually to butter and sugar mixture and add lemon juice.
Fold in ground almonds until fully combined.
Spread jam evenly on the pre prepared pastry base.
Spoon in sponge mixture and gently spread evenly in the tin.
Bake in the oven for 35-40 minutes until it is a light golden brown. remove from the oven and leave to fully cool before starting the icing.