Using a food processor, blend the ground pistachio and confectioners’ sugar together, about 2 minutes, until the mixture is well blended and well combined. Sift it, adding in the ground cardamom and set aside.
Heat your egg whites in a microwave for 15 seconds. Then, using a stand mixer, beat the egg whites until they’re foamy. Gradually add the granulated sugar, about 1 TBS at a time, still whisking, until the whites reach medium soft peaks. Add the almond extract and the food coloring, if you’re using it, and whisk until well incorporated.
Sprinkle half of the pistachio mixture over the beaten egg whites and fold until just incorporated. Then add the rest, folding until everything is combined. Tap the bottom of your mixing bowl against the counter to eliminate any air bubbles.
Transfer the batter to a pastry bag and pipe the mixture onto a parchment lined baking sheet. Each cookie should be 1.5? in diameter and at least 1/2? apart.
Allow the cookies to rest for at least 30 minutes, until they are no longer tacky when touched. At this point, you should preheat your oven to 300 degrees F. You can also make the Rosewater Icing (recipe follows).
Bake, rotating halfway through, until macarons are slightly firm to the touch and can be lifted from the parchment, 20-25 minutes. Remove from the baking sheets and allow to cool completely.
In a heatproof bowl set over simmer water, combine the egg whites, rosewater, red food coloring, if you’re using it, and the granulated sugar. Cook, whisking constantly with a handheld electric mixer, until the sugar has dissolved and the mixture is warm to the touch.
Remove the egg-white mixture from the heat and beat it on high speed until it holds stiff peaks. Then, continue beating until the mixture has cooled and is fluffy, about 5-7 minutes.
At this point, add in the confectioners’ sugar, mixing to combine.
Once your icing has set and your cookies have cooled sufficiently, you can begin assembling your macarons. To do this, spread approximately 2 teaspoons of icing on the flatsides of half of the cookies. Sandwich with the other halves, keeping flat sides down.
Refrigerate until firm, about 20 minutes. As noted above, these taste even better after a day, but if you can't wait that long, I certainly won't judge you.