Whisk flour, salt, and baking powder together in a small bowl.

Cream the softened butter and sugar in a large bowl with a hand mixer (or a stand mixer on medium speed using the paddle attachment) for 3-5 minutes, until fluffy.

Add egg and vanilla, and beat until smooth.

Mix in the dry ingredients until just incorporated.

Dump out onto a lightly floured surface and divide in half. Form each half into round disks, about 1-2 inches tall. Then wrap in plastic wrap and chill in the refrigerator for about an hour, until firm.

Preheat your oven to 350 degrees and line 2 baking sheets with parchment paper.

When the dough is firm, take out your first disk, and sprinkle your counter with flour.

Roll out dough using plenty of flour on both the counter and your rolling pin. Flip the dough over frequently and re-flour it, making sure that it doesn't stick to the counter. If it does, you will have a terrible time getting the cookies off the counter and onto your baking sheet. Use a bench scraper to loosen the dough if it sticks. Stop rolling when the dough is about ¼ inch thick.

Cut out as many cookies as you can, transferring to a parchment-lined baking sheet as you go.

Combine the scraps into another disk and put back in the fridge to firm up, while you roll out the 2nd disk of dough from the fridge. You can re-roll the scraps once more, but that's it. After that, the cookies will come out tough and not as tasty.

Bake cookies for 10-12 minutes, until the edges turn golden. Let cookies sit on baking sheet for 1-2 minutes after you take them out of the oven, then transfer to a cooling rack.