Evenly pour the granulated sugar into a glass or ceramic baking dish.
Toast the sugar until lightly golden, for about 45-60 minutes, stirring after every 15.
Let the sugar cool completely. Reduce the oven temperature to 300F.
While the sugar cools, place the egg whites into the bowl of a stand mixer fitted with a whisk attachment. Let sit at room temperature for 30 minutes.
Once cool, place the sugar into the bowl of a food processor to break up any clumps that formed during baking.
In medium size bowl, sift together the toasted sugar, cream of tartar and salt. Set bowl aside.
In a separate large bowl, sift together the powdered sugar and almond flour. Process the remaining large pieces in a food processor to pulverize them, then sift. Set the bowl aside.
Line half baking sheets with parchment paper, or macaron guide silicone mats. Or place templates under the parchment, if using.
Beat the egg whites on medium speed until foamy.
Beat in the toasted sugar, cream of tartar and salt mixture.
Whip the egg white mixture until stiff peaks form. The meringue will stand up straight when the whisk is removed. The egg white mixture will be thick and glossy.
Remove the bowl from the stand mixer. Remove the bowl from the stand mixer and folding in the almond flour mixture. The egg whites will deflate a bit and that is ok. The batter is ready when it "ribbons", which means it falls off the batter in a stream. You should be able to make a "8" with the batter falling off the spatula. This means the batter is ready. You're looking for about 50-75 folds. Check for the ribboning after every 15-20 seconds.
Fill a piping bag fitted with a round tip (Wilton 1A or 2A) and pipe 1 ½" rounds on the parchment paper.
Firmly tap the pans on the counter 2-3 times to remove air bubbles. Let the macarons sit until just slightly tacky, but no batter comes off on your fingers, about 30 minutes.
Bake the macarons for 20 minutes. Cool completely.
Vanilla Bean Buttercream
In the bowl of a stand mixer fitted with the paddle attachment, whip butter for 6-8 minutes on medium speed. Butter will become very pale and creamy.
Add the powdered sugar, cream, vanilla bean paste and salt. Mix on low speed for 1 minute to incorporate the ingredients.
Increase the speed to medium and whip for and additional 5-7 minutes. Frosting will be light, creamy and fluffy.
Assemble the Macarons
Spoon the buttercream into a piping bag fitted with a round piping tip ( I used a Wilton #12).
Flip half of the macaron shells over, flat side up. Pipe a mound of buttercream in the centers of the flipped shells.
Place the remaining macaron shells on top of the cookies with filling and squeeze gently, until the filling just reaches the edges.
Toasted sugar vanilla macarons can be stored in the refrigerator in an airtight container for up to 5 days. Bring to room temperature before serving.