Age your egg whites at least 24 hours ahead of time. Separate the eggs, place the whites in a clean bowl, and refrigerate them uncovered overnight.

Combine the almond flour, pistachio flour, and powdered sugar in a bowl. Whisk briefly, then sift the mixture into a large bowl.

Pour the aged egg whites into a clean bowl and start beating on medium speed until foamy and opaque. Add the cream of tartar, then gradually add granulated sugar, beating until you reach stiff peaks.

Fold the sifted dry ingredients into the meringue using a silicone spatula in a macaronage technique until the batter flows off the spatula in a thick ribbon.

Transfer the batter to a piping bag fitted with a round tip. Pipe rounds about 1.5 inches in diameter on parchment-lined baking sheets.

Let the piped shells sit at room temperature for 30–60 minutes until a skin forms.

Preheat your oven to 300°F (150°C) and bake the shells for 14–16 minutes.

Cool the shells completely on a flat surface before attempting to peel them.

For the buttercream, beat softened butter until light, then add powdered sugar in two additions, raspberry puree, vanilla, and salt. Beat until smooth.

Match shells by size, pipe buttercream on one flat side, and gently press a matching shell on top.

Refrigerate assembled macarons for at least 24 hours before serving.