Preheat the oven to 350°F (175°C).

Line two baking sheets with parchment paper and set aside.

In the bowl of a food processor, combine the confectioners' sugar and almond flour.

Pulse until finely ground.

In a separate mixing bowl, beat the egg whites with an electric mixer until soft peaks form.

Gradually add the granulated sugar, continuing to beat until medium-stiff peaks form.

If using, add food coloring at this stage and mix until combined.

Carefully fold the dry almond flour mixture into the meringue until the batter is smooth and shiny.

Transfer the batter into a piping bag fitted with a 1/2" tip.

Pipe the batter onto the prepared baking sheets in 1" circles, spacing them about 1" apart.

Firmly tap the baking sheets on the countertop a few times to release any air bubbles.

Bake in the preheated oven for 15-18 minutes, until the macarons are set and can be easily lifted off the parchment paper.

Let the macarons cool completely on the baking sheets.

Once cooled, fill with Italian buttercream and sandwich the cookies together.

Store the filled macarons uncovered in the fridge for 1-2 days before consuming.

Filled macarons can be frozen for up to 1 month.