Heat your oven to 350°F.

In a food processor: Combine the flour, salt, and sugar in the bowl of a food processor. Add butter and vanilla to the bowl, then run the machine until the mixture forms large clumps — just keep running it; it might take another 30 seconds for it to come together, but it will.

Transfer dough to a 10-inch round or 9-inch square tart pan with a removable bottom set and press the dough evenly across the bottom and up the sides. Transfer to freezer for 15 minutes, until solid.

Once firm, prick all over with a fork. Coat a piece of foil with nonstick spray, and press it oiled-side-down tightly against the frozen crust, so it is fully molded to the shape. Bake tart with foil (no pie weights needed) for 20 minutes, then carefully, gently, a little at a time, peel back foil and discard. Return to oven for 10 to 20 minutes (keep an eye on it, I overbaked mine!), until lightly browned all over. Let cool to room temperature, ideally, but it’s okay to use if it’s still lukewarm.

Remove the zest of 4 limes with a vegetable peeler or zester/rasp, being careful to avoid the white pith. Squeeze the limes to make 1/2 cup of juice and set the juice aside. Put the zest in a food processor fitted with a steel blade. Add the sugar and salt and process for 2 to 3 minutes, until the zest is very finely minced. Add butter and blend until fully disperse into the sugar. Add eggs, two at a time, and blend to combine. Add lime juice and blend for a second or two.

Transfer the filling to a medium saucepan and cook over low heat, stirring constantly, until thickened, about 5 to 10 minutes. The lime curd will thicken at about 175°F, or just below a simmer. Remove from heat and pour into the tart shell. Transfer to the fridge to cool and set.

Add dolloped of lightly sweetened whipped cream (if you wish) and serve cool, in wedges or squares.