Heat oven to 325℉.
Line 2 sheet pans with parchment paper. Set aside.
In a medium bowl, beat butter and sugar with an electric mixer until light and fluffy, about 1-2 minutes.
Beat in egg white and vanilla.
Add flour, salt, and baking powder.
Mix on low just until combined.
Form into a ball.
Turn out onto a piece of parchment paper.
Place another piece of parchment on top.
Roll to 3/16 inch thickness.
Cut out cookies.
Remove excess dough.
Gently lift cookies and place on prepared pans.
Gather scraps and re-roll until all dough is used.
Bake for 17 minutes, until just starting to color around edges.
Allow to cool on pan.