This pie owes its distinctive character to the citrus variety called the Key lime, which, while not native to Florida, is called the Key lime in the United States because it has been grown in the Florida Keys since the 1800s. Bottled Key lime juice is perfectly acceptable when fresh Key limes are not available, or, in a pinch, just use regular limes (but don’t tell anyone). Read About Meringue.

Line a 9-inch pie pan with:

Bake the crust as directed in About Blind Baking Crusts or About Crumb Crusts.

Reduce the oven temperature to 325°F. Whisk together in a medium bowl until well blended:

Pour the filling into the pie crust. If not topping the pie with meringue, bake the pie until the center looks set but quivers when the pan is nudged, 15 to 17 minutes. Let cool completely on a rack, then refrigerate for up to 1 day. Serve with:

If topping the pie with meringue, bake the pie until the filling thickens just enough to support the topping, 5 to 7 minutes, but no longer. Meanwhile, prepare:

Spread a band of meringue around the perimeter of the filling, anchoring it to the crust at all points. Dollop the remaining meringue over the center and smooth the top. Bake the pie until the meringue is browned, about 20 minutes more. If using Italian meringue, you may also brown it with a propane torch instead of in the oven, but first bake until the filling is set. Let cool completely on a rack, then refrigerate for up to 5 days.