Preheat the oven to 180C/350F degrees.
Mix the almond flour, baking powder and salt together.
In another bowl mix the butter, water, eggs, erythritol and vanilla essence.
Combine the wet and dry ingredients together and stir well.
Pour the mixture into a muffin tin lined with cupcake cases.
Bake for 20 to 25 minutes until firm.
Allow to cool, then with a small knife, cut out circles from the cupcakes. Turn the circles on their sides and trim down slightly, (so that they will fit better on the cupcake). Cut in half.
Fill the holes in the cupcakes with the lemon curd.
Place the two cut circle halves on top of the cupcake, with the longside next to each other...making the "butterfly" wings.