Step 1

Place sugar and ⅓ cup water in a small saucepan. Cook over medium-low, swirling pan occasionally, until sugar is dissolved and syrup registers 240°F on an instant-read thermometer, 10 to 14 minutes.

Step 2

Meanwhile, after about 7 minutes of cooking sugar syrup, beat egg whites with a stand mixer fitted with a whisk attachment on medium speed until foamy, about 30 seconds. Add cream of tartar and salt. Beat until soft peaks form, 1 to 2 minutes.

Step 3

With mixer running on medium speed, gradually stream hot sugar syrup into whipped egg white mixture. Continue beating until meringue is glossy and forms stiff peaks and the outside of mixer bowl has cooled slightly, 3 to 5 minutes. Reduce speed to low, and beat in vanilla extract. Proceed with desired baked meringue recipe.