01 - Line two baking sheets with parchment paper or silicone mats. Fit a piping bag with a round tip, approximately 1 centimeter in opening.
02 - In a food processor, pulse almond flour and powdered sugar until exceptionally fine. Sift the mixture into a large bowl, discarding any remaining coarse particles.
03 - In a meticulously clean, grease-free bowl, whip the egg whites and cream of tartar until foamy. Gradually incorporate the granulated sugar, continuing to whip until stiff, glossy peaks form. Add a few drops of pink gel food coloring and mix until the color is evenly distributed.
04 - Delicately fold the sifted almond mixture into the meringue in three separate additions. Use a spatula to gently fold until the batter achieves a thick, flowing ribbon consistency, often referred to as 'lava' consistency. Exercise caution not to overmix.
05 - Transfer the prepared batter to the piping bag. Pipe 1.2-inch (3-cm) rounds onto the lined baking sheets, ensuring approximately 0.8-inch (2-cm) spacing between each. Firmly tap the trays on the counter to release any trapped air bubbles. Puncture any visible surface bubbles with a toothpick.
06 - Allow the piped macaron shells to rest uncovered for 30 to 45 minutes, or until the tops are dry to the touch and a light skin has formed.
07 - Preheat your oven to 300°F (150°C). Bake one tray at a time for 12 to 15 minutes, rotating the tray halfway through the baking process. The shells should develop 'feet' at the base and avoid browning. Cool the shells completely before carefully removing them from the trays.
08 - For the buttercream filling, beat the softened butter until light and creamy. Gradually add the sifted powdered sugar, mixing until the mixture is fluffy. Incorporate the strawberry puree, vanilla extract, and a pinch of salt. Beat until the buttercream is smooth and uniform.
09 - Pipe or spoon the prepared buttercream onto the flat side of half of the macaron shells. Top with the remaining shells to create sandwich cookies.
10 - Refrigerate the assembled macarons in an airtight container for a minimum of 24 hours to allow them to mature and for the flavors to meld. Bring them to room temperature briefly before serving for optimal texture and taste.