Preheat oven to 350° F. Line baking sheets with parchment paper or a nonstick baking mat, such as a silicone mat.
Cream together room-temperature butter and sugar with a stand mixer or hand mixer in a large bowl until light and fluffy (about 3 minutes).
Then add egg and mix until well combined. Scrape down the sides of the mixing bowl to be sure the butter and sugar are well combined.
Stir in flour, baking powder, and salt, and combine these dry ingredients.
Then, gently stir in vanilla extract into the cookie dough.