Prepare your equipment and workspace. Line two baking sheets with silicone mats or parchment paper. Prepare a piping bag with a round tip (about ½ inch/1.25cm diameter). Ensure your mixing bowl is completely clean and free from any grease.
Process dry ingredients thoroughly. In a food processor, pulse together the almond flour, powdered sugar, dried dill, and garlic powder until very fine. Sift this mixture twice to remove any lumps.
Whip the egg whites to perfection. In a clean bowl of a stand mixer with whisk attachment, beat egg whites with a pinch of salt on medium speed until foamy. Gradually add granulated sugar and increase to high speed, beating until stiff peaks form (when you lift the whisk, the peaks should stand straight without flopping over).
Fold in dry ingredients with care. Add about one-third of the almond mixture to the whipped egg whites and fold gently with a spatula. Continue adding the remaining mixture in two more batches. Add food coloring if using. The batter should flow like lava when lifted with a spatula—when dropped, it should settle back into itself within about 20 seconds.
Pipe uniform circles onto prepared sheets. Transfer batter to the piping bag and pipe 1.5-inch rounds onto the prepared baking sheets, leaving about 1 inch between each. Tap the sheets firmly against the counter several times to release air bubbles.
Rest the shells before baking. Let the piped macarons rest at room temperature for 30-45 minutes until they form a skin—when you lightly touch one, it shouldn’t stick to your finger.
Bake at the right temperature. Preheat oven to 300°F (150°C) and bake one sheet at a time for 15-18 minutes. The shells should rise with “feet” at the bottom. Allow to cool completely on the baking sheet before removing.
Prepare the salmon filling while shells cool. In a medium bowl, mix softened cream cheese until smooth. Fold in the chopped smoked salmon, fresh dill, lemon zest, lemon juice, capers (if using), and black pepper until well combined. Taste and adjust seasoning if needed.
Assemble your macarons with care. Match macaron shells of similar size. Pipe or spoon a small amount of salmon filling onto the flat side of one shell, then gently press another shell on top to create a sandwich.
Refrigerate to develop flavors. Place the assembled macarons in an airtight container and refrigerate for at least 24 hours to allow flavors to meld and textures to develop. Bring to room temperature for about 30 minutes before serving.