1 3/4 cups confectioners' sugar
1 cup superfine almond flour (such as Bob's Red Mill)
3 large egg whites, at room temperature
1/4 teaspoon cream of tartar
Pinch of salt
1/4 cup superfine sugar
4 drops green, orange or yellow gel food coloring
3/4 teaspoon pure lime, orange or lemon extract
3/4 cup citrus curd or preserves
Preheat the oven to 325 degrees F (or 300 degrees F for convection). Line 3 baking sheets with silicone baking mats. Sift the confectioners' sugar into a large bowl. Whisk in the almond flour.
Beat the egg whites, cream of tartar and salt in a stand mixer with the whisk attachment on medium speed until frothy, about 1 minute. Increase the speed to medium high and gradually beat in the superfine sugar until the mixture is just stiff and shiny, 2 to 2 1/2 more minutes, adding the food coloring and extract during the last 15 seconds of mixing.
Fold the egg white mixture into the almond flour mixture using a rubber spatula, giving the bowl a quarter turn with each fold, until incorporated. Continue folding and turning, scraping down the bowl, until the batter is smooth and falls off the spatula in a thick ribbon, no more than 2 minutes (about 60 strokes).
Transfer the batter to a piping bag fitted with a 1/4-inch round tip. Holding the bag perpendicular to and 1/2 inch above the prepared pans, pipe 11/4-inch rounds (30 to 35 per pan). Firmly tap the baking sheets twice against the counter to release any air bubbles. Let the cookies sit at room temperature until the tops are no longer sticky to the touch, 30 to 40 minutes, depending on the humidity.
Slip another baking sheet under one batch of macarons (a double baking sheet protects the cookies from the heat). Bake the macarons, rotating the baking sheet halfway through, until the tops of the cookies are shiny and rise 1/8 inch to form a "foot," about 20 minutes. Transfer the top pan to a rack to cool completely. Repeat with the remaining two batches, using a double baking sheet for each. Sandwich the cookies with citrus curd or preserves. (The cookies will be crisp on top. For a softer texture, sandwich the cookies and let sit 4 to 12 hours before serving.)
Silicone baking mats make all the difference for these macarons ¿ we found they help the cookies rise evenly.