Beth's Foolproof Macarons: Shatter Crisp

Instructions:

1. Combine almond flour and powdered sugar in a sifter and sift them together into a large bowl, discarding any oversized almond chunks.
2. Preheat oven to 300°F (150°C) and ensure the oven rack is in the center position.
3. Beat egg whites and cream of tartar on medium speed until frothy.
4. Gradually add granulated sugar one tablespoon at a time while continuing to beat.
5. Increase speed to medium-high and beat until the meringue is glossy and forms stiff peaks. Stir in vanilla extract and optional gel food coloring.
6. Gently fold the dry ingredients into the meringue using a 'cut and fold' motion with a spatula.
7. Continue folding until the batter reaches a lava-like consistency, where the batter falls in a thick ribbon that disappears back into the bowl after 10-15 seconds.
8. Transfer batter to a piping bag and pipe 1.5-inch circles onto silicone baking mats or parchment paper.
9. Firmly tap the baking sheet on the counter 3-4 times to release air bubbles.
10. Let the macarons rest at room temperature for 20-30 minutes until a skin forms and the batter no longer sticks to the touch.
11. Bake for 15-20 minutes until set.
12. Prepare buttercream by beating softened butter, powdered sugar, heavy cream, and vanilla extract until smooth, then pipe between cooled shells.