Key limes are one of those citrus fruits that are only sold in grocery stores during certain months. This is because they have thinner skin and don’t keep as long as other varieties. But, they also have a more intense flavor than Persian limes- the latter being the variety that’s available year-round in the supermarket. You can make this recipe with either variety and both will yield that slightly floral, tart flavor that limes are loved for. But, if you can find key limes then use those for a more intense flavor.

These little limes get their name from Florida keys, but originally they were known as Mexican limes. After a particularly harsh winter in 1894-95, they were planted to replace the damaged lemon trees. In the 1920s they were largely replaced by the hardier Persian limes and today key limes are quite the treat.

To begin making this recipe you’ll need to create a shortbread crust. A short pre-bake ensures the crust will be completely cooked through after the filling is added.

Once you’ve got your filling made and poured into the warm crust bake for another 25 minutes or until the center is no longer jiggly.

The hardest part of making sure you give these bars enough time to set up. If you skimp on the chill time then you can end up with runny bars- still delicious but far stickier to eat.

Dust with powdered sugar and then cut into squares. I cut mine into 25 because I knew these would be very more-ish and very rich, but you can make your squares any size you’d like.

The shortbread melts in your mouth, while the delicate flavor of the zest reveals hidden depths to these limes. This is must-try recipe for shortbread fans and those who love all things citrus.