Preheat your oven to 180°C and line a loaf tin with baking paper.
To make the shortbread base, beat the butter and sugar together until pale and fluffy. Add the egg yolks and kafir lime shreds and beat again until well combined. Stir through the flour, baking powder and pinch of salt until it forms a dough. Press into the loaf tin and bake for 15 minutes or until golden and cooked through.
To make the coconut topping, whisk the egg white until soft peaks form then slowly add the sugar. Continue to whisk until the peaks stiffen. Fold through the coconut.
Spread the jelly over the pastry base evenly then cover with the coconut egg white mixture - spreading this evenly too. Bake for 20 minutes until golden.