In a large bowl or with your stand mixer cream the powdered sugar and butter until it is fluffy. If using the stand mixer it will take about 5 minutes.
Once the sugar and butter is creamed together, add in the egg and vanilla extract.
In a medium sized bowl mix the flour, baking powder, and salt. Use a whisk to mix everything together thoroughly.
Slowly add the flour mixture to the sugar, butter, egg and vanilla extract mixture. Mix everything until well incorporated.
Put a handful of the freshly made dough between two sheets of parchment paper and roll until you get your desired thickness and set aside still on the parchment paper.
Repeat with the rest of the sugar cookie dough.
Put the rolled dough including the parchment paper, on a cookie sheet and refrigerate for 30 minutes.
After your dough has been rolled out and refrigerated for half an hour cut your cookies with the cookie cutter from the dough.
Place the cookies onto a sheet pan lined with parchment paper or a silicone mat, bake at 350 for 8 to 10 minutes or until the cookies have browned on the edges.
Move the cookies to a cooling rack and allow them to completely cool.
When your cookies are cooling prepare your royal icing.