Remove egg whites from the fridge and allow them to come to room temperature.
Prepare all your equipment. Place your template on the baking tray and then cover with a layer of baking paper, then place to the side. Next insert the piping tips into the piping bags and cut off the narrow ends and place these to the side too. Finally wipe down your electric mixer and bowl with lemon juice,
Place the egg whites into the bowl and begin to whip them with your electric mixer on low speed.
Once the eggs start to look frothy, add the cream of tartar.
Continue mixing until the eggs look foamy, then gradually add the caster sugar, 1 tablespoon at a time, mixing well after each addition until all the sugar has been incorporated.
Turn the mixer up to medium-high and continue to whip the meringue until it reaches soft peaks.
Add the vanilla extract and continue whipping the meringue until it reaches stiff peaks and all the sugar has dissolved.
Once you have reached stiff peak stage it is time to combine the almond flour/icing sugar with your meringue. You want to do this while keeping as much air in the meringue as possible. Best method to achieve this is to add half the almond flour to your meringue and gently fold in - aka use your spatula to scrape around the outside of the bowl until this first batch of almond flour has been mixed in). Then, fold in remaining almond flour using the same technique. Be careful to not overmix the batter.
Divide the batter equally into 3 bowls (if you want to be precise you can use your kitchen scales to measure the weight of each portion).
Add the food colouring to each bowl, then mix it in. Gently press the batter against the side of the bowl as you mix in the food dye. Keep mixing the batter in this way until it reaches the consistency of hot lava, and falls off your spatula in a long ribbon shape.
Spoon the batter into the prepared piping bags. You'll need one piping bag for each colour.
Pipe your batter onto the prepared baking trays. To achieve even circles hold the piping bag straight over the tray with the tip hovering about a centimeter above the baking paper. Squeeze the bag so that the batter comes out the end, then stop squeezing and gently lift the piping bag away from the tray. If you find the baking paper is moving, you can place a dab of batter underneath the baking paper in each corner to stick it to the tray.
Once you have piped all the macarons out, pick up your baking tray and bang it on the counter a couple of times. This will help the macarons to flatten out and encourage any air bubbles to rise to the surface.
Check the surface of the macarons for any air bubbles. If you find any, pierce them with a toothpick, then use the toothpick to flatten out the surface of the macaron once again.
Rest the macaron cookies by leaving the trays on the bench until the tops of the macarons feel dry to touch. The amount of time this takes will depend on the weather in your area. Where I am in Melbourne, it takes about 20mins most days. You'll know the macarons are ready to bake if they feel smooth and dry to touch.
Preheat oven to 110 degrees. Transfer the tray of macarons to the oven. Bake at 110 degrees Celsius for 18 minutes (or a little longer if you are using a silicone mat instead of baking paper). You can check if they are cooked by gently lifting them off the paper, if they come lift up easily in one piece, then they are cooked.
Leave the macarons on the tray until it has cooled completely, then transfer the macarons to a wire rack.
Sort through macaron cookies to match them up into similar size/shaped pairs.
Choose the "prettier" macaron in each pair and add any decorations you would like. You can try drizzling some melted chocolate over them and adding sprinkles or dried edible flowers.
Once the decorations have set, place the macarons in a single layer in an airtight container. If you need to layer macarons on top of each other place a sheet of baking paper between each macaron so they don't stick together. Place this container in the fridge.