In a food processor, combine the almond flour, icing sugar and salt and pulse together (this helps the shell be light and crunchy). Sift into a bowl and set aside.
In a mixer bowl combine the egg whites and cream of tartar and beat until soft peaks form, about 2 minutes. Meanwhile, combine the white sugar and 1/4 cup water in a small saucepan over medium high heat. Add food colouring and heat until the sugar reaches the soft ball stage (113 degrees C). With the mixer running, pour in the syrup and beat until stiff peaks form and the mixture is glossy.
Spoon the meringue into the bowl full of dry ingredients and fold to combine. Spoon the batter into a pastry bag. On a baking tray lined with baking paper, pipe out small circles a few centimetres apart. Bake 15 minutes to dry them out, then increase temperature to 180 degrees C and bake just until firm, about 10 minutes. Let cool about 1 hour before filling.
Preheat the oven to 95 degrees C.
In a saucepan whisk together the lemon juice, zest, eggs, egg yolks and sugar until smooth. Cook over medium heat, stirring constantly, until it boils. Whisk 1 minute while boiling. Strain into a bowl to remove any cooked eggy bits. Chill overnight.
Fill a piping bag with the lemon filling and pipe on to one biscuit then top with another to make a macaron.