Combine powdered sugar and almond flour in a food processor. Process for 30-40 seconds, or until mixture has a very fine and light texture.
Whip egg whites with an electric mixer on medium-high speed until soft peaks form. With mixer running, slowly add granulated sugar and vanilla. Continue whipping until stiff peaks form.
Gently fold almond flour mixture into egg whites, being careful not to overmix. The final mixture should be smooth and glossy.
Line two baking sheets with parchment paper or silicon baking mats. Transfer macaron batter to a piping bag with a small round tip. Pipe 2-inch circles, about an inch apart, on both baking sheets. Tap baking sheets against the counter to release air bubbles.
Let the macarons shells rest in a dry place for 20-30 minutes, or until you can touch the shells without the batter sticking to your fingers.