1 8 inch graham cracker crustor 9 ¼-cup capacity graham cracker tartlet crusts or ramekins--see note
Filling
14ouncessweetened condensed milk1 can
4large egg yolks
1/2cupfresh lime juicefrom key limes or regular limes
2tfine lime zestno white
Meringue
4egg whites
½teaspooncream of tartaroptional
2/3cupsugar
1/2teaspoonvanilla
Instructions
Make filling and bake pie
Whisk together condensed milk, egg yolks, juice (add half at a time) and zest until well combined.
Pour filling into crust(s) and bake at 350 F for 15 minutes for full pie, 10 minutes for tartlets. Cool pie completely on rack (filling will set as it cools), then chill (see note).
You can stop here and serve a regular key lime pie. Otherwise...
Top with meringue
In a medium-sized, heatproof mixing bowl, whisk together the egg whites, sugar, vanilla and cream of tartar (optional).
Place the bowl over a small pan with simmering water, making sure the water doesn't touch the bowl.
Whisk the mixture at least until the sugar has fully dissolved. If you want to pasteurize the meringue, keep whisking until the mixture reaches a temperature of 160°F. Take off the heat.
Using a hand held or a stand mixer, beat the warm mixture until the meringue holds a medium peak and has cooled to room temperature.
Fill a piping bag, then pipe on top of a pie or tartlets.
Brown with torch, then serve or refrigerate until needed.
Notes
I used Keebler mini-graham crusts. You can cool pie in freezer for about 10 minutes before topping with meringue if you are in a hurry A microplane is the best tool for zesting.
I am not a health professional and nutrition data is calculated programatically. Accuracy may vary with product selection, calculator accuracy, etc. Consult a professional for the best information.