Pre-heat the oven to 180°C.
Grease and line a 23cm / 9 inch square tin.
Place all the cake ingredients into a mixer or use a hand mixer and mix until well combined.
Tip into the tin and spread out to the edges and level with a palette knife.
Bake for about 35 minutes until springs back to touch or an inserted skewer comes out clean.
Allow to cool in the tin for 5 minutes before turning onto a rack to cool.
Make the icing by mixing in enough of the lime juice to make a pourable but not too runny icing (or it will run off the cake).
Pour onto the cake and allow to spread.
If you have any more limes you could decorate with some zest.