Step 1

Making the syrup: Mix granulated sugar, cream of tartar, and ¼ cup of water. Boil in a saucepan over medium-high heat. If you have a candy thermometer (Amazon affiliate link) -I do recommend using one- boil until it reaches 112 °C [235 °F]. If you do not have a thermometer, boil until it reaches a syrup consistency (It will be thick but still a light color, see notes)

Step 2

Whisking egg whites: In the meantime, using the stand mixer wire attachment, whisk the egg whites for 30 seconds at low speed. Increase speed to medium and whisk until they become white and has doubled and formed peaks (about 3 mins).

Step 3

Adding syrup: Slowly, and in a thin stream, pour the syrup into the bowl while whisking over high speed until it forms very firm peaks (about 5 mins).

Step 4

Finishing: Add the vanilla extract, and once incorporated, the powdered sugar, whisk until it's combined and the meringue is at room temperature. The meringue should have firm peaks, and some of the meringue has "climbed" into the center of the wire whisk.

Step 5

Storing: It can last a few hours well covered and refrigerated. If you notice that it starts to form a crust, add a few drops of lime juice, and incorporate with a spatula.