In the bowl of a food processor, combine the powdered sugar, almond flour, and ½ tsp of salt, and process on low speed until extra fine. Sift the almond flour mixture through a fine mesh sieve into a large bowl.
In a separate bowl, beat the egg whites and the remaining ½ tsp of salt with an electric hand mixer until soft peaks form. Gradually add the granulated sugar until fully incorporated. Continue to beat until stiff peaks form.
Add the vanilla and beat until incorporated. Add the food coloring and beat until combined.
Add about ⅓ of sifted almond flour mixture at a time to beaten egg whites and use spatula to gently fold until combined. After the last addition of almond flour, continue to fold slowly until the batter falls into ribbons and you can make a figure 8 while holding the spatula up.
Transfer the macaron batter into a piping bag fitted with a round tip.
Place 4 dots of the batter in each corner of a rimmed baking sheet, and place a piece of parchment paper over it, using the batter to help adhere the parchment to the baking sheet.
Pipe the macarons onto the parchment paper in 1½ inch circles, spacing 1-inch apart.
Tap the baking sheet on a flat surface 5 times to release any air bubbles
Let the macarons sit at room temperature for 30 minutes to an hour, until dry to the touch
Preheat oven to 300 degrees
Bake the macarons for 17 minutes, until the feet are well-risen and macarons don't stick to the parchment paper.
Transfer macarons to a wire rack to cool completely before filling.
In a large bowl, add the butter and beat with a mixer for 1 minute until light and fluffy. Sift in the powdered sugar and beat until fully incorporated. Add the vanilla and beat to combine. Add the cream, 1 tbsp at a time, and beat to combine.
Transfer buttercream to a piping bag fitted with a round tip.
Add a dollop of buttercream to one macaron sheet. Top with another macaron shell to create a sandwich. Repeat with remaining macaron shells and buttercream.
Recipe by the minimalist table at https://www.daraboxer.com/theminimalisttable/french-macarons/