Preheat oven to 325 degrees.
Beat butter and sugar, until light and fluffy.
Add in egg, egg yolk, and vanilla.
In a seperate bowl, whisk flour, baking powder, and salt.
Mix in flour mixture in two parts. Mix until just combined.
Use 1/4 of the dough and roll to a 1/4 inch thickness on a floured surface. Cut out cookies and bake for 11-13 mintues
Prepare royal icing. Whisk the merigue powder and water for 3 minutes until foamy. Add powdered sugar and whisk until you have stiff peaks. Tint as needed with gel colors. Thin with water to get desired consistency.