Preheat oven to 350 degrees Fahrenheit

Grease and line the base and sides of a 7-inch springform tin with a baking paper

In a food processor, add the flour, 2.5 oz of butter and 1 slightly beaten egg.

Pulse until it's crumbly.

Divide the dough into two.

Press one half of the dough into the base of the tin and set aside.

Prepare the lemon curd by placing 1/2 cup lemon juice, 1/2 cup powdered sugar, slightly beaten egg and 2.5 oz butter in a saucepan.

Stir continuously until thickened, on low heat.

Pour the lemon curd onto the cake base.

Top with the remaining crumble mix.

Bake until golden brown for 30 minutes.

Cool and remove from springform tin

Dust with confectioners sugar and serve.