Method
Preheat the oven to 160°C/310°F/gas 2½ and grease a 24cm loose-bottomed cake tin. Put your biscuits into a food processor and whiz until you've got really fine crumbs, then mix in your melted butter. If you don't have a food processor, just wrap your biscuits in a tea towel and bash them up with a rolling pin until fine. Spread the biscuit mixture around the base of your greased tin, making sure you get it right to the edges, then press it with your hands to pack it down. Place the tin on a baking sheet and pop it into the fridge while you make the filling.
Whiz the cream cheese in a food processor until smooth, then gradually add the sugar. Add the eggs one at a time, mixing well after each one. Pour in the lime juice and vanilla seeds or extract and whiz again until just combined. Again, if you don't have a food processor, just do this by hand. Don't worry if the mixture seems too thin – it's supposed to be like that. Tip it over your chilled biscuit base, spread it out evenly, and bake in the oven for around 45 to 55 minutes – you want the cheesecake to still have a slight loose wobble. Remove from the oven and set aside for 15 minutes to cool slightly. Turn the oven up to 220°C/425°F/gas 7.
To make the meringue topping, put your egg whites into a clean bowl and beat until they form soft peaks – an electric whisk is quite handy here. Gradually add the caster sugar and beat until thick and glossy. Finally, fold in the coconut. Spoon this meringue mixture on to the middle of the cooled cheesecake and spread it to the edges, using the back of a spoon, so it just covers the filling. It should be about 2cm thick. I like to make a few ripples and peaks in the top so it looks impressive. Bake in the oven for 5 minutes, or until the meringue is starting to turn golden in colour and is crisp to touch. Let it cool down, then place it in the fridge for a few hours (this is important) to chill before serving.
Carefully remove it from the tin, transfer it to a nice platter and sprinkle over the lime zest. Really nice served with mango, strawberries and raspberries when they're in season.