First Step: Prepare your workspace and ingredients by sifting almond flour and powdered sugar to remove lumps and achieve a fine texture. Separate egg whites and allow them to reach room temperature for better meringue.

Second Step: Whisk egg whites until foamy, then gradually add granulated sugar and beat to stiff peaks, forming the meringue base for the macaron shells.

Third Step: Gently fold the sifted almond flour and powdered sugar into the meringue using a spatula, combining without deflating the mixture to create the perfect macaron batter.

Fourth Step: Transfer the batter into a piping bag and pipe uniform circles onto a baking sheet lined with parchment paper. Tap the tray to remove air bubbles and let them rest for 30-60 minutes to form a skin.

Fifth Step: Bake in a preheated oven at 150°C (300°F) for 15-18 minutes. Adjust baking time slightly for vegan or gluten-free variations as needed.

Sixth Step: While shells bake, prepare the filling by mixing softened butter with key lime juice and powdered sugar until smooth and creamy.

Seventh Step: Allow baked shells to cool completely before pairing and filling with the key lime butter cream to assemble the macarons.

Final Step: Refrigerate assembled macarons for at least an hour to allow flavors to meld, then serve chilled or at room temperature as preferred.