Preheat oven to 200 degrees F (95 degrees C). Line a baking sheet with parchment paper.

Beat egg whites in a bowl until they form soft peaks; beat cream of tartar and vanilla extract into egg whites. Gradually beat white sugar into mixture until meringue forms stiff peaks. Transfer 1/4 of the meringue mixture into a separate bowl. Beat red food coloring into remaining 3/4 of meringue.

Transfer colored meringue into a piping bag fitted with a round tip. Pipe 20 Santa hat shaped triangles, about 1 1/2 inch tall and bending over at the tips, onto the parchment paper-lined baking sheet. Sprinkle the hats with red sugar.

Transfer remaining 1/4 uncolored meringue into a clean piping bag fitted with a round tip. Pipe little white pom-poms onto each hat tip and a small edging of fluffy white trim onto the bottom of each hat.

Bake meringue cookies in the preheated oven until hard but not browned, about 1 hour and 20 minutes. Turn off oven and let cookies cool inside oven until crisp, 1 hour.