Grease and line the base and sides of your 18cm (7 inch) round loose-bottomed or springform cake tin before you start so that it's ready to go when you need it.
Make the lime sponge batter
Preheat the oven to 180C (160C fan).
To make cake batter, start by placing the caster sugar and softened butter in a large mixing bowl. Beat with an electric whisk or by hand until pale and fluffy.
Add the two eggs and beat again until combined.
Add the self-raising flour and fold through with a wooden spoon or silicone spatula - I prefer to use a spatula and it makes it easy to scrape the bottom of the bowl and make sure nothing is missed.
Add the juice and zest of two limes. See notes on lime sizes below. Gently fold through to combine.
Spoon the batter into your prepared cake tin and level off.
Bake for about 25 minutes or until firm all the way across. Check that it's cooked through by pushing a. skewer al the way into the centre - it should come out clean.
Make the lime drizzle
You can make your lime drizzle icing towards the end of the sponge's baking time.
Start by putting the zest of 2 limes and juice of 3 limes into a small, microwave safe bowl. Remember again that my limes may vary in size to yours and adjust accordingly.
Add the icing sugar and gently mixing together until there are no lumps.
Place the bowl in the microwave for 60 seconds on full power.
Carefully remove the bowl from the microwave - it will be very hot. The syrup should change from opaque to translucent and be slightly thickened. If it's not, give it another 30 seconds. If you don't have a microwave you can do this on the stovetop.
Bring your lime drizzle cake together
When your cake come out of the oven, give it 5-10 minutes to cool a little, then prick it all over with a skew, going almost to the bottom each time.
Pour the hot lime drizzle syrup over the cake and allow it to sink in.
Sit your lime drizzle cake on a wire rack and leave it to cool completely in it's tin before removing and serving.
Enjoy your gorgeously zesty lime drizzle cake, with a sticky, sweet and sour top.
My limes weighed about 55-65g (about 2 ounces) each and yielded 20-25ml (3/4 fl oz) juice per lime. If yours are bigger or smaller, adjust accordingly. Once your luscious lime drizzle cake has cooled you can store it in a sealed container. There's no need to keep it in the fridge, just make sure it's in a cool spot out of direct sunlight. In a cool cupboard or in the pantry will work perfectly. This lime drizzle will keep for 3-4 days. As there is quite a lot of moisture in the cake, I find it is best enjoyed on the first day or two after baking.