Preheat oven to 200°C.
Combine flour, cocoa, caster sugar and baking powder in a large bowl and mix well. In a separate bowl combine eggs, orange rind and macadamias and mix well. Make a well in the centre of the dry ingredients, pour in the egg mixture and stir to form a dough.
Turn dough onto a lightly floured surface and divide in half. Shape halves into logs, place on a greased and floured baking sheet and bake for 15 minutes.
Remove from oven and when cool enough to handle cut logs into 0.5cm thick slices. Place slices on baking sheets and bake a further 10 - 15 minutes. Cool on a wire rack then store in an air tight container.