Preheat oven to 350 degrees (325 degrees on convection setting).
Place sugar and butter in bowl of electric mixer with paddle attachment. Cream until smooth.
In a small bowl, beat eggs and vanilla together until mixed well.
Add egg mixture to creamed sugar in electric mixer. Mix on low until combined.
In a large bowl, whisk together gluten free flour, cocoa powder, salt and baking powder.
Add dry ingredients to electric mixer. Mix on low until incorporated. Scrape down sides and mix again.
Divide dough in half. On a Silpat mat, roll half of the dough between 2 pieces of parchment paper. Using ¼" thick dough rolling guides will ensure even thickness of cookies. Place on baking tray and put in freezer for 15 minutes to chill. Repeat with other half of dough.
Remove dough from freezer. Peel off top sheet of parchment paper to loosen from dough. Replace top sheet of parchment paper; gently flip over. Repeat peeling off top sheet of parchment paper and set aside.
Cut cookie shapes with your favorite cookie cutters. Place on cookie sheet lined with parchment paper. Do not to overcrowd to prevent cookies from spreading during baking.
Bake for 10-12 minutes (6-8 minutes on convection setting); rotating half way through baking time. Cool on cookie sheets. Decorate with royal icing when cool to the touch.