Method

• 1.
  Place orange in a small saucepan of boiling water (top with a small saucer if necessary to keep submerged). Boil for 1 hour or until very soft when tested with a skewer, then remove from heat. Drain and cool completely. Place orange in KitchenAid food processor and whiz until a smooth puree. Transfer to a bowl. Wipe processor clean.
• 2.
  Preheat the oven to 160°C. Grease and line the base and sides of a 15cm round cake pan with baking paper.

• 3.
  Place macadamias and plain flour in the food processor and whiz to a meal. Transfer to a bowl with the caster sugar and butter, then, using your hands, rub in the butter until the mixture resembles coarse crumbs.
• 4.
  Whisk yoghurt and eggs together with the orange puree. Add to the macadamia mixture and gently stir until combined. Pour into prepared pan, smoothing the top. Bake for 1 hour 45 minutes or until golden and just firm to the touch. Cool completely in the pan, then invert onto a wire rack to cool completely.
• 5.
  For the brown butter icing, place butter in a pan over high heat and cook for 5 minutes or until nutty brown. Cool completely, then whisk in the icing sugar and 2 tbs water. Set aside to thicken and cool slightly.
• 6.
  Pour icing over the cake and scatter with macadamias to serve.