In a mixing bowl or food processor, combine the butter and sugar and beat until the butter is creamy.

Add the flour and baking powder. Combine everything using the paddle attachment of your mixer.

After that, stir in the vanilla extract and mix to create a dough.

Divide the dough into 12 mini tart pans with removable bottoms.

It must be tightly formed and pressed to the bottom up to the sides of the tart pan.

Bake it in a preheated oven of 350'F for 8 minutes.

Let it cool completely before adding your filling.

Set it aside while you do the filling.

In a medium saucepan, combine all the ingredients (apart from the butter) and cook, stirring frequently. This process will take about 10 minutes until the mixture thickens. Do this process until the mixture coats the back of your spoon. Continue to simmer and stir.

Add cold butter one piece at a time, and whisk it in thoroughly before adding the next.

Take the lemon curd out from the heat, strain it through a fine mesh sieve, and discard the particles.

Add the lemon curd into your baked shortbread crust and even out the top using a spoon.

While making the lemon curd, let the egg whites warm up to room temperature. Whip egg whites with the cream of tartar and mix them on high speed until soft peaks form.

Beat until stiff peaks form, while gradually the sugar.

Transfer meringue in a piping bag with a star tip and pipe it on top of your tart with lemon curd filling.

Bake lemon meringue tarts until golden brown, for about 12 minutes.

Let it cool completely before serving.