Whisk the ingredients, excluding the butter, until smooth.
Place over low heat. Stir constantly with a wooden spoon until the mixture thickens, about 5 minutes. Turn to low and add the butter. Stir until smooth. Pour into a bowl, cover and refrigerate for at least 1 hour.
Once the crust and curd have cooled, spoon and smooth one layer of the lemon curd and then the lime curd should be layered on top of the lemon curd. Shake a light dusting of powdered sugar over the lime curd.
Refrigerate for 1 hour – cut in two inch squares and serve
On low, process all of the ingredients.
Press mixture evenly into the bottom of an un-greased 9 x 13 inch pan.
Gently press the fork tines into the dough in three rows throughout the top of the pressed the dough.