Line two large baking sheets with baking parchment
Sieve the almond flour and powdered sugar into a large bowl
Place the eggs whites into a stand mixer and start to whisk on medium until they become foamy and opaque between 1-2 minutes
Add the cream of tartar and whisk for a further 5-6 minutes before slowly adding the sugar one tablespoon at a time beating for at least 30 seconds between each spoonful allowing it to dissolve
Continue whisking until you have soft peaks, a further 6-7 minutes
Add in the food colouring until you have your desired colour
Continue whisking until you have stiff and glossy peaks
Gently fold in the almond sugar mixture to the egg mixture – approximately 50 folds until you have a batter that is thick but which runs off the spatula continuously
If it is not quite ready, fold another five times then check again and continue with this process until you have the perfect batter
Be careful not to over mix or it will become too runny!!
Pour into a piping bag with 3/8 inch round tip and holding the bag at a 90 degree angle , steadily squeeze the batter onto the baking sheet until you have a one inch circle
Stop squeezing and twist the bag to detach the batter
Repeat piping leaving one inch between each circle until the sheets are full
Tap the sheets on the counter top to remove any air bubbles – pop any remaining bubbles with a toothpick
Set aside uncovered for between 35-45 minutes until a skin has formed on the top of the macarons – they should be dry to touch when ready
Place in the oven preheated to 325 f and bake for 10-12 minutes until they have puffed up
Place the whole parchment sheet onto the cooling rack immediately to allow to cool, do not leave to cool on the baking tray
For the buttercream, place the softened butter into the bowl of a stand mixer and beat until light and fluffy. Slowly add in the powdered sugar and as it thickens add in the fresh lime juice and vanilla extract.
Beat until combined and you have a smooth buttercream.
Place the buttercream into a piping bag.
Overturn half of the cooled macarons and pipe the buttercream onto the flat surface. Do not over fill or go too close to the edge or the buttercream will spill out when the top is added.
Place the remaining macarons on top of the filled halves and press gently.
Sprinkle with a little lustre dust.
These will keep in an airtight container for two days