Unlike traditional Key Lime Pie which is delicious but heavily loaded with calories, this light and luscious version substitutes ricotta and fat-free condensed milk for the usual full-fat stuff.
I used the larger Persian limes here which is why ‘Key Lime’ doesn’t appear in the title – and the buttery crust with polenta and lime zest also makes a nice change from the ubiquitous graham cracker base and only takes a minute or two to prepare.
This recipe is more delicate than its traditional cousin due to the addition of beaten egg whites so it will be all puffed-up when you first take it out of the oven. Then, like a souffle in a cold breeze, it will promptly collapse and possibly crack on the surface after a few minutes but this in no way detracts from the light and fragrantly limey end result.
Once it’s cooled, chill in the fridge and dust with powdered (icing) sugar to serve.
For the crust –
3 oz (85g) of all-purpose/plain flour
1 ½ oz (43g) of fine ground polenta/cornmeal
2 oz (57g) of fine white sugar
3 oz (85g) of unsalted butter, melted
½ teaspoon of grated lime zest, chopped
For the filling –
3 eggs, separated
1 can of fat-free condensed milk
1 ¼ cups (300ml) of Ricotta (preferably home made) – full fat or semi skimmed
The juice of 2 large limes
The finely grated zest of 1 large lime
To prepare the crust –
Preheat the oven to 350F (180C)
Whisk all the dry ingredients together then add the lime zest and melted butter – combine with a fork and press into the base and up the sides of a 9-10 inch (228-250cm) loose-based tart tin.
Bake for approx 20 minutes or until golden. Cool.
For the filling –
In a bowl, combine the egg yolks, condensed milk, Ricotta, lime juice and zest. Whisk the egg whites together until they form stiff peaks and fold a quarter of them into the filling to lighten it.
Using a large metal spoon, gently fold the remaining egg whites into the filling and with a cutting motion – combine everything well.
Spoon the filling into the cooled base and bake at 375F (190C) until puffed and golden – approx 25 minutes.
Cool the tart then chill in the fridge – dust with powdered sugar to serve.
Can be made 24 hrs ahead.