Make-ahead: You can prepare the lime zest, wrap in cling film and chill, and make cake the day before stored in a lidded container.
Make the icing a few hours ahead and keep covered with cling film placed directly on the surface.
Using a zester remove long fine strips of zest from the lime, place in a small pan of boiling water and blanch for 1 minute. Drain in a small sieve under running cold water and pat dry with kitchen paper. Wrap in cling film and set aside for the decoration.
Heat the coconut milk in a small pan until it just comes to the boil. Remove, add the desiccated coconut, squeeze the lime and also add. Leave to soak and allow the coconut to soften for 1 hour.
Preheat the oven to 180°C/Fan160°, 350°F, Gas 4.
In a mixer beat the butter and Tate & Lyle Golden Caster Sugar for about 5 minutes until light and fluffy. Add the eggs little by little, scraping down the sides once or twice, for about 5 minutes, until smooth and creamy.
Sift the flour and baking powder together, then fold one-third into the creamed mixture along with one-third of the coconut milk mixture. Repeat until both are used up and you have a smooth mixture. Divide between the cake tins where the mixture will come halfway up the sides. Level the tops with a palette knife.
Bake the cakes on the middle shelf of the oven for about 35-40 minutes until risen, golden and when a fine skewer poked into the centres comes out clean. Leave to cool in their tins for 15 minutes, then turn out onto a wire rack to completely cool. Remove the parchment.
Meanwhile, put the remaining 15ml (½floz) of coconut milk in a mixing bowl, sift over the Tate & Lyle Fondant Icing Sugar, stir well, then mix in the lime juice to make a pouring consistency.
Put one of the cakes on a serving dish, spread with the whipped cream, spoon on the mango-passion fruit jam, then place the second cake on top.
Drizzle the icing over the cake allowing it to trickle down the sides. Scatter with the reserved lime zest, then leave the icing to firm up for about 30 minutes and serve.