Preheat the oven to 250 degrees F. Line 2 baking sheets with parchment paper. Beat the egg whites and salt in a large bowl with a mixer on medium speed until frothy (use the whisk attachment if using a stand mixer). Add the cream of tartar; increase the speed to medium high and add the superfine sugar, 1 tablespoon at a time. Scrape the seeds from the vanilla bean into the meringue (or add the extract) and continue beating until the sugar is dissolved and the meringue is thick, glossy and forms stiff peaks, about 6 minutes.
Fit a piping bag with a large star tip. Fill the bag with the meringue and pipe spirals on the prepared baking sheets, about 1 inch apart. Sprinkle with the coarse sugar.
Bake 1 hour, then turn off the oven and let the meringues stand in the oven until dry, about 2 hours. Store in an airtight container up to 1 week.