Preheat the oven to 350 degrees Fahrenheit.
In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
2 1/2 cups all-purpose flour, 1/2 teaspoon baking powder, 1/2 teaspoon salt
In the bowl of a stand mixer with the paddle attachment (or in a large bowl with a hand mixer), cream the butter and sugar together for about 3 to 6 minutes, until it is light and fluffy. Then add the vanilla and one egg at a time, combining for about thirty seconds after each addition.
2 cups sugar, 16 tablespoons unsalted butter, 2 teaspoons vanilla extract, 2 large eggs
Add the flour mixture. Turn the mixer on low. As soon as the flour has begun to incorporate, turn the mixer on high. The goal here is to combine the flour with as little mixing as possible to not activate the gluten.
Press the cookie dough into the bottom of a 9x13 inch pan and bake for about 20 minutes. Let it cool on the counter for about 10 minutes, and then put it in the refrigerator for a half hour.