2 2/3 level cups of plain flour
1 cup of room temp unsalted butter (I reckon this is about 3/4 of a 250g pack)
1 large lemon
pinch of salt
2/3 cup of icing sugar.
Cream the sugar and butter and salt together. Then add the flour and zest of the lemon and combine, if a bit too dry use the juice from the lemon to bind.
Either pat into a tin at about 1/2 cm thickness, or roll out to said thickness and use cutters to make shortbread buscuits.
My oven is fierce, so I had it set at 160 and these cooked in 8mins. For a normal oven probably about 180 for a similar time.