Whisk egg whites until they begin to foam, about 1 minute. Slowly add in granulated sugar and continue to whip until stiff peaks form (mixture should be thick and glossy; you should be able to hold the bowl upside down without the whites falling out).

Add sifted confectioners’ sugar, almond meal, and food coloring to the mixture. Using a spatula, fold until it is well incorporated and the mixture has a consistency of molten lava. To test, scoop up a spoonful of batter and drop it back into the mixture; it should flatten and disappear into the batter in about 15 seconds or so. If it doesn’t, continue folding the mixture. It should take about 50-60 strokes for the batter to reach the right consistency.

Transfer the mixture to a piping bag fitted with large round tip, and pipe small rounds onto a baking sheet lined with parchment paper with a template underneath. The rounds should be no larger than 2 inch in diameter with at least ½ inch of space between.

Gently tap the bottom of each sheet on work surface to release trapped air, then let the macarons dry on the counter for about 30 minutes until a skin is formed on the surface (the batter shouldn’t stick to your hand when you touch it).

Place the macarons in a 350F oven and bake for about 10-12 minutes until the shells harden. Let cool completely on the baking sheets.

In the top of a double boiler filled with 2 inches of simmering water, combine egg yolks, confectioners’ sugar, lemon juice and zest. Cook over moderately low heat, whisking constantly, until thickened, about 10 minutes.

Remove from the heat and whisk in the butter. Strain the curd into a bowl and press a sheet of plastic wrap directly onto the surface. Refrigerate until completely cold.

Match the macaron shells in pairs. Pipe a small round of lemon curd (about half a teaspoon) on the flat side of a macaron shell and sandwich together with a matching macaron shell. Repeat with the remaining macarons.