Preheat oven to 250°. Line 2 rimmed baking sheets with parchment paper.
In a large bowl, beat together egg whites and cream of tartar with a mixer at high speed until soft peaks form. Gradually add granulated sugar, confectioners’ sugar, and salt, and beat until mixture is thick and creamy, approximately 5 minutes. Add peppermint extract and desired amount of food coloring, beating to combine.
Transfer egg white mixture to a pastry bag fitted with a large star tip (Ateco #847). Using an upright motion, pipe egg white mixture onto prepared baking sheets, pulling up tip in three motions to create a Christmas tree shape.
Garnish each tree shape with a sprinkle of pearlized sugar, if desired.
Bake for 1 hour. Turn oven off, and let meringues stand in oven overnight to continue drying out.
Store in an airtight container.
Notes
Since humidity will affect meringues, bake them when the air is dry.
Recipe by TeaTime Magazine at https://teatimemagazine.com/christmas-tree-meringues/