In a large mixing bowl, beat 1 cup of softened unsalted butter with 1 cup of sugar until creamy and light, about 3-4 minutes. Add in 1 egg and 1 teaspoon of vanilla extract, mixing until well combined.

In a separate bowl, whisk together 2 cups of all-purpose flour, ½ teaspoon of kosher salt, and ½ teaspoon of baking soda. Gradually add this dry mixture to your butter mixture on low speed.

Divide the dough into three equal portions. Color one third with red gel food coloring and another with green. Wrap tightly and refrigerate for at least 1 hour.

Roll each colored dough portion out between two sheets of parchment paper into 7-inch squares. Chill again in the refrigerator for about 15 minutes.

Peel parchment paper from each layer. Stack the red, green, and plain squares, then tightly roll into a log shape and freeze for 1 hour.

Preheat the oven to 350°F (175°C). Remove the log and slice into 1/3-inch thick rounds. Roll edges in red sanding sugar.

Bake cookies for 8-10 minutes until set but not browned. Allow cookies to cool for 1 minute on the sheet before transferring to a wire rack.