Preheat oven to 140C Fan/160C/325F/Gas Mark 3 and line cupcake tin with cases.
Cream baking spread and caster sugar until fluffy.
Add eggs, mix well.
Gently fold in self-raising flour and lemon zest.
Divide mixture into cases, bake for 25-30 mins until skewer comes out clean, then cool on a rack.
Use cupcake corer or knife to make hole in each cupcake.
Fill holes with lemon curd.
For buttercream, mix softened butter, icing sugar, lemon extract, and milk until smooth. Pipe or spread onto cupcakes.
Decorate with lemon slices and sprinkles.
Store in airtight container, consume within 3 days.