If you're using a macaron template, place it on a baking tray and place a layer of baking paper on top. Then put the tray aside.
Put the almond flour, confectioner's sugar and beetroot powder (if using) in a food processor and pulse for a minute. This will mix everything together and break down any large pieces of almond flour.
Transfer the mixture to a sieve and sift it into a bowl. Then set it aside while you make your meringue.
Pop the egg whites in a clean bowl. Using either a hand held electric mixer, or a stand mixer fitted with the balloon whisk attachment, whip the egg whites at medium speed until they start to look foamy.
Add the cream of tartar, and continue to whip for a minute.
Gradually add the caster sugar to your egg whites while you continue to whip the eggs using your mixer. I tend to add about a tablespoon or so every 15-30 seconds. Once all the sugar has been incorporated, add the salt and vanilla extract to the eggs.
Turn the mixer to high and whip until the mixture looks white, and marshmallow like. You'll know it's done when it is thick enough that when you scoop some up with a spoon it forms a stiff peak shape.
Add half the dry ingredients to the meringue and use a rubber spatula to gently fold it into the meringue. Then add the remaining dry ingredients and fold this in as well.
Next deflate your meringue until it loosens slightly. Best method I've found is to use your spatula to spread the batter around the side of the bowl, then scrape it back off the sides and into the middle. Repeat this action until the macaron batter loosens and becomes glossy. Test the consistency by scooping the batter up with your spatula and letting it slowly drop back into the bowl. It is ready if it flows of your spatula in a ribbon shape.
Spoon the batter into a piping bag, fitted with a round tip.
Hold the piping bag over the baking tray and squeeze the bag until a circle of batter (about 1.5 inches wide) is piped onto the tray. Repeat this process until all your macaron cookies have been piped onto the tray.
Bang the tray on your counter a couple times to encourage any air bubbles to rise to the surface. If you can see any air bubbles on the macarons, use a tooth pick to pop them. Then place your tray on the counter for 20-30 minutes to let the macarons dry slightly.
Your macarons are ready to bake when they have a matt texture and feel dry to the touch. Bake at 280 F (140 C) for 20-25 minutes. You will know they have baked once they have risen and look firm (but have not browned). If they look jiggly when you go to take the tray out of the oven, continue to bake them. You can also test if they are ready by peeling a macaron off the baking sheet. If it comes off in one piece and the bottom is dry, they are ready.
Allow your macarons to cool on the tray before transferring them to an airtight container.