Preheat a convection oven to 75°C. Line a baking tray with non-stick baking paper and prepare a piping bag with a large fluted nozzle.
Beat egg whites until they form stiff peaks. As the mixer is still beating, gradually sprinkle in sugar. Beat on high speed for no less than 10 minutes to dissolve all the sugar crystals.
Fold in lemon zest, and then drizzle meringue with food colouring. Spoon into piping bag without mixing in the colouring to create a yellow streak effect.
Pipe 3cm rounds onto baking paper and bake in oven for 2 hours or until the meringues dry out completely.
When cool, sandwich together the meringues with the Tatua Mascarpone and serve.