Add the butter and sugar to the bowl of a stand mixer and beat on medium speed for 3–4 minutes until creamy.

Add the egg and vanilla extract, mixing well and scraping the bowl as needed.

In a separate bowl, whisk together the flour, salt, and baking soda.

With the mixer on low, slowly add the dry ingredients to the wet ingredients until fully combined.

Divide the dough into three portions. Tint one portion red, one green, and leave the third plain.

Shape each into a ball, wrap in plastic, and refrigerate for 1 hour.

Roll each dough ball between two sheets of parchment into a 7-inch square. Chill again.

Stack the dough layers—red, green, white—then roll into a 12×8-inch rectangle.

Remove the top parchment and roll tightly into a log. Freeze for 1 hour.

Preheat oven to 350°F. Line baking sheets with parchment.

Slice the log into ⅓-inch pieces and roll edges in red sanding sugar.

Bake 8–10 minutes or until set. Cool completely on a wire rack.