Set oven racks in upper and lower third of oven*. Preheat oven to 225 degrees. Line two rimmed 18 by 13-inch baking sheets with parchment paper.
Add egg whites to metal or glass mixing bowl of electric stand mixer** if you haven't already. Add cream of tartar and vanilla extract.
Set mixer with a whisk attachment and whip mixture on medium speed to soft foamy peaks, about 1 minute. Then while mixing on medium speed over the course of about 1 minute, slowly dust in granulated sugar and add salt.
Increase mixer speed to high and whip until very thick glossy peaks form, this will take several minutes.
Transfer half of the mixture to a piping bag fitter with a large star tip*** (I like to use Ateco 826 - 829 tips depending on desired shape).
Pipe meringue into rounds or tear drop shapes about 1 1/4-inches wide, and spacing each about 1-inch apart. Repeat with remaining mixture.
Transfer baking sheets to racks in preheated oven. Bake 30 minutes then switch and rotate baking sheets and continue to bake 30 minutes. Turn oven off and leave meringues in warm oven to rest 1 hour (or 2 hours on humid day).
Remove from oven and let cool at least 10 minutes before serving. Store in an airtight container at room temperature, free from moisture.
*Note that every oven is different, my oven tends to brown on top more than is standard so I usually try to put one rack near center and one in lower third but not right on bottom rack.