Sift together powdered sugar, cinnamon and almond flour in a large bowl.
With an electric mixer beat the egg whites at high speed until foamy. Add the granulated sugar and continue beating until stiff peaks form. Add the food colouring and beat just for a few seconds, until absorbed.
Gradually fold the almond-sugar mixture into the egg whites, using a rubber spatula. Keep folding until the mixture thinners a bit without becoming too liquid. Avoid mixing too much or too little: the consistency of the macarons should not be too liquid (overmixed) or too thick (not mixed enough).
Pipe circles onto trays lined with baking sheets or silicon mats and then leave the shells to dry out for 30-40 minutes.
Preheat the oven to 150 degrees C. Bake the macaron shells for 10-15 minutes. They should be dry and should be removed easily from the paper. If you are not sure in your oven, you can start from 120 degrees and gradually increase the temperature while the macarons are growing. In this case you have to watch them all the time.
Let the baked shells stay for 5 minutes on the baking trey before transferring them to a wire rack.