With an electric mixer, beat the egg whites until soft peaks start to form. Beating all the while, add the cream of tartar and vanilla extract, then slowly add the 1/2 cup of sugar. Continue to beat until the peaks stiffen.
Spoon the meringue into a quart-size plastic bag. Snip off a corner and pipe 2 dozen 1 1/2-inch-tall Santa hat triangles onto a parchment-lined baking sheet (you should have about 1/4 of the meringue left).
Sprinkle the triangles with the red sugar, then use the remaining meringue to give each one a pom-pom and trim.
Bake the hats until they're hard but not browned, about 1 hour and 20 minutes.
Turn off the oven and leave the hats in it for an hour to crisp before removing.