Pre-heat your oven to 160C Fan/350F/Gas Mark 4 and grease and line two 8" cake tins (that are at least 2" deep)
To make the sponge, mix together the caster sugar and baking spread using an electric mixer until it is light and fluffy, about 3 minutes
Whisk in the eggs and lemon curd until well combined
Then gently mix in the self raising flour
Finally, fold in the lemon zest
Divide the mixture between the tins. You can do this by eye, or use scales for accuracy
Bake them for 35-40 minutes or until they are golden brown and a skewer inserted in the middle comes out clean
Once the sponges are baked, remove from the oven and leave to cool for 15 minutes in the tin. Then run a butter knife around the edges of the tin to loosen them, then carefully tip them out onto a cooling rack and leave to cool completely
To make the filling use an electric mixer to whisk together the mascarpone cheese, double cream, vanilla extract and icing sugar until thick
Put one of the sponges on your chosen cake stand or serving plate and spread half of the mascarpone cream all over it
Then spread half of the lemon curd over it
Top with the second sponge and spread the remaining mascarpone on top of the cake
Drizzle or spoon over the remaining lemon curd, letting it drip down the sides
Serve immediately. Store leftovers in an airtight container in the fridge and eat within 2 days