Place the butter, flour, baking powder and salt in a food processor and process until the mixture resembles wet sand.

Add the sugar and blitz again then add the egg, vanilla and lemon zest and process until it forms a dough.

Take it out of the mixer and roll out on a lightly-floured surface until it is 1cm thick and a rectangular shape.

Sprinkle the crushed macadamias over the top and then roll it up from a long side to form a log.

Wrap it in plastic wrap and refrigerate for 30 minutes (optional - I didn't and they were perfect but if it's really hot you probably want to do this step).

Pre-heat the oven to 170C fan-forced and line a baking tray with baking paper.

Slice the dough up into 1cm slices and place on the baking tray leaving 2cm between each one.

Bake for 10-15 minutes or until they start to turn golden.