Prepare your workspace and preheat the oven to 300°F (150°C). Sift together 1 cup of almond flour and 1 cup of powdered sugar into a bowl.

In a clean mixing bowl, beat 3 room-temperature egg whites on medium speed. Gradually add ¼ cup of granulated sugar until stiff peaks form.

Gently fold the sifted almond flour and powdered sugar mixture into the egg whites using a spatula. Add gel food coloring if desired.

Transfer the macaron batter into a piping bag and pipe small circles on a baking sheet lined with parchment paper.

Allow the piped macarons to rest at room temperature for at least 30 minutes, until a skin forms.

Bake the macarons in the preheated oven for 15 minutes, avoiding opening the oven door during the first 10 minutes.

To prepare the buttercream filling, beat ½ cup of softened unsalted butter until creamy. Gradually add powdered sugar, vanilla extract, and heavy cream or milk.

Once the shells are cool, flip half of them upside down and pipe or spread the buttercream onto these shells, topping with the remaining shells.