Preheat over to 220°C
Sift flour and salt into a large bowl, stir in the sugar and lemon myrtle. Rub in butter with your fingertips until mixture resembles fine breadcrumbs. Stir through the macadamias.
Make a well in the centre and pour in the buttermilk and fold through. Turn onto a floured surface and knead lightly. Pat dough out to approximately 2cm thickness and cut into rounds with a 5cm cutter, dip the cutter into the flour each time before cutting.
Place close together on baking tray lined with non-stick baking paper. Brush tops with a little milk and bake for 10 minutes or until golden.