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1. Prepare the Baking Sheets: Line two baking sheets with parchment paper or silicone baking mats. If desired, trace circles on the parchment paper for uniform macaron sizes.
2. Sift the Dry Ingredients: In a medium bowl, sift together the almond flour and powdered sugar. Set aside.
3. Whip the Egg Whites: In a clean, dry mixing bowl, add the egg whites and a pinch of salt. Beat on medium speed until frothy.
4. Add Cream of Tartar: Once frothy, add the cream of tartar and continue beating until soft peaks form.
5. Gradually Add Granulated Sugar: Slowly add the granulated sugar while beating. Increase speed to high and beat until stiff peaks form and the mixture is glossy (about 5-7 minutes).
6. Add Vanilla and Food Coloring: Gently fold in the vanilla extract and food coloring (if using) into the meringue.
7. Incorporate the Dry Ingredients: Gradually fold the sifted almond flour and powdered sugar mixture into the meringue until the batter flows like lava and can form a figure-eight without breaking.
8. Piping the Macarons: Transfer the batter to a piping bag fitted with a round tip. Pipe small circles onto the prepared baking sheets, leaving about 1 inch of space between each macaron. Tap the sheets gently to release air bubbles.
9. Rest the Macarons: Let the piped macarons sit at room temperature for 30-60 minutes, or until a skin forms on the surface.
10. Preheat the Oven: Preheat your oven to 300°F (150°C).
11. Bake the Macarons: Bake for 15-20 minutes, ensuring they do not brown. They are done when they have formed a “foot” and can be lifted off the parchment easily.
12. Cool the Macarons: Remove from the oven and let cool on the baking sheets for about 5 minutes before transferring to a wire rack to cool completely.
13. Beat the Butter: In a mixing bowl, beat the softened unsalted butter until creamy and smooth, about 2-3 minutes.
14. Add Nutella: Add the Nutella to the butter and mix until well combined.
15. Incorporate Powdered Sugar: Gradually add the powdered sugar, mixing until smooth. If desired, add heavy cream for a softer filling and mix until combined.
16. Assemble the Macarons: Pair the macaron shells and pipe or spread the Nutella filling onto the flat side of one shell, then sandwich with another shell.

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