My grandmother (Nana Duckless, we called her) taught me to make these when I was about six: they are easy to make and the best part is that you can use your favourite jam for the centre.
Preheat the oven to 180degC. Lightly grease several baking trays or line with non-stick baking paper.
Cream the butter, sugar, vanilla essence and lemon rind then beat in the egg. Add the sifted flours, then add a tiny squeeze of lemon juice.
Using teaspoons of the mixture, roll into small balls with lightly floured hands (don't make them any bigger than this because they spread).
Place onto the prepared trays, leaving room between each for spreading. Here's the fun part: make a small indent in each one using the pointed end of an egg then fill the hollow with jam.
Bake in the oven until pale gold, about 15 - 20 minutes. Remove from oven then slide off the trays using a spatula.