In a large mixing bowl, beat the softened unsalted butter with granulated sugar and brown sugar until light and fluffy, about 2–3 minutes. Add the egg and vanilla extract, and mix until fully combined.

In another bowl, whisk together all-purpose flour, baking powder, and salt. Gradually add the dry mixture to the butter mixture and stir until just combined.

Wrap the dough in plastic wrap and refrigerate for at least 30 minutes.

Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper. Scoop tablespoon-sized balls of dough and place onto the baking sheet, spacing them 2 inches apart. Bake for 8-10 minutes or until the edges are golden brown.

Allow cookies to cool on the baking sheet for about 5 minutes before transferring to a wire rack to cool completely.