Mix butter with sugar, add zest and juice
Add the flour and salt
(by now the dough should be SUPERsilky smooth)
Make 1inch sausages
Roll them in plastic foil, leave in the fridge for at least an hour
Preheat the oven to 200C
Cut them up in 1/2inch tranches
Bake in the oven for about 20min, or until deemed ready.