I make a lime pie that is so easy.
I buy a pre made tart case (yep, I cheat!)
In a mixing bowl add a can of condensed milk and the juice of 2-3 limes as well as the zest from 2 limes. The mix will thicken whilst you're stirring. Add it to the tart case and put it in the fridge to set.
That's it! Easy peasy and soooooo yummy!