Preheat the oven to 180℃ / 356℉. Prepare a 9 x 9-inch baking tin (or any shape you prefer) and line with baking paper.
Blend the coconut biscuits until fine by either using a blender or place the biscuits in a zip lock bag and crush using a rolling pin.
Add the biscuits and melted butter to a medium bowl and mix until well combined.
Prepare a baking tin (I used a 9inch square pan or a round tin/springform tin with 23cm radius) with cook and spray or baking paper.
Firmly press the base into the tin with the edges rising about an inch or so. Place in the fridge while you make the filling.
In a medium bowl whisk together the egg yolk and condensed milk until well combined. Add the fresh lemon juice - you may add an additional tbsp or two if you'd like it to be extra lemon(y).
Bake for 15mins at 180 degrees celisus. Meanwhile make the whipped egg whites.
Add 3-4 egg whites (I used 4) to a large bowl. Add the cream of tartar and start whisking, gradually start adding in the sugar as your whisking. Lastly add in the vanilla essences and continue whisking until stiff peaks have formed.
Remove the tart form the oven. Sift the cornstarch over the lemon filling (this'll help the meringue adhere to the filling). Dollop the whipped egg whites on top of the warm filling using a spoon or a piping bag. Feel free to get creative.
Pop the tart back in the oven and bake for another 10mins until golden brown on top. Allow to reach room temperature before serving. You could also pop it in the fridge for 15minutes. This will allow the base to firm up a bit quicker. Once it's firmer, remove from the baking tin, slice and devour!