Preheat oven to 200°F. Line baking sheets with parchment paper or a silpat.
Beat egg whites with a hand mixer on high speed until they start to create bubbles. Add cream of tartar and salt and continue to mix.
Once the egg whites start to form soft peaks, add vanilla and slowly start incorporating sweetener in small amounts. Mix until stiff peaks start to form.
Add mixture to a piping bag with a star tip and pipe onto the prepared baking sheet.
Place meringues in the oven and cook for 50-55 minutes. Turn oven off and open the door slightly letting meringues cool inside for 1-2 hours.