Preheat oven to 180°C and grease a 22cm non-stick cake tin with butter.
Crush roasted macadamia nuts in a food processor and set aside.
Peel mangoes and dice the flesh, saving as much juice as possible, then reserve some nice pieces of mango (about 85g) and puree the remaining mango flesh with all the reserved juice. You should have about 1 cup of mango puree.
Beat softened butter and vanilla essences with half the sugar. Beat until thick and pale. While beating, add remaining sugar and beat until all sugar has been added. Add eggs, one at a time, and beat well after each addition.
In a separate bowl, combine crushed nuts, flour and baking powder.
Remove the bowl from the mixer and add the flour mixture, stirring well to combine. Add the mango puree and mix gently.
Spoon the batter into the prepared tin, then sprinkle chopped macadamia nuts and reserved diced mango over the batter and swirl through.
Bake for 1 hour, then remove the cake from the oven and cool in the tin. When cool, remove from the tin and dust with icing sugar.
