For the passion fruit lime tartlets, first prepare the batter: Beat butter and sugar until fluffy. Stir in the yolks, cardamom and lime zest. Add the mixture with a pinch of salt to the flour and knead the whole thing into a smooth dough. Shape into a ball, wrap with plastic wrap and refrigerate for 1 hour.
Roll out the dough on a floured work surface. Cut out circles the size of the cake pans and line the pans with them. Bake in the preheated oven at 180 °C for about 8 minutes, making sure that the dough does not get too dark.
For the passion fruit-lime curd, strain the passion fruit into a puree. Rinse the limes with hot water and pat dry. Squeeze the juice and finely grate the zest from one lime.
Place fruit puree, lime juice and zest, butter and sugar in a bowl and beat in a double boiler until butter is melted. Add eggs and beat until mixture thickens slightly – this will take about 10 minutes.
Spread the passion fruit lime curd on the cake layers. Sprinkle the passion fruit lime tarts with powdered sugar.