Preheat the oven to 350 degrees F. Line 2 baking sheets with parchment paper.
Using a hand or stand mixer, cream the butter and sugar on medium speed until fluffy, about 2 minutes.
Add the egg and vanilla and mix until smooth, about 2 minutes.
In a separate bowl, combine the flour, baking powder and salt.
Add the dry mixture to the butter mixture. Reduce the mixer speed to low and mix until just combined, about 30 seconds.
At this point if the dough feels warm, refrigerate it until chilled, about 15 minutes.
When the dough feels cool to the touch, scoop out teaspoon-size balls and drop them on the prepared baking sheets. The dough should yield 4 dozen balls.
Bake until golden, 12 to 15 minutes.
Let cool.
