In a bowl, add the cookie dry ingredients (gluten free flour and sugar) and whisk to blend.
In a small bowl, add softened butter and vanilla. Mix well.
Pour the wet ingredients into the dry ingredients and mix. Take the dough ball and wrap it in plastic wrap. Chill for 45 minutes.
Preheat the oven to 350º F.
Remove the dough ball and roll the dough out flat.
Use cookie cutters to cut shapes. Place the shapes on a parchment lined baking sheet and bake for 8 minutes.
Remove the cookies and cool on a cooling rack.
Time to make royal icing!
In a mixer, add powdered sugar, egg whites, cream of tartar and salt.
Turn the mixer on SLOW. (If you turn it on too fast, it will explode sugar everywhere!)
Slowly mix the icing for 9 minutes until it becomes somewhat fluffy and thick.
Decorate your cookies, don't forget to let each color icing dry before adding another color, otherwise the colors can run together.