Preheat your oven to 350°F (175°C) and line an 8x8 baking dish with parchment paper or aluminum foil.

Cream together 1/2 cup unsalted butter and 1/4 cup granulated sugar until pale and fluffy. Gradually add 1 cup sifted flour and salt, pulsing until crumbly. Press this into the bottom of the baking dish and bake for 12-15 minutes until golden.

In another bowl, whisk together 2 eggs and 1 cup passion fruit purée until combined. Gradually add 1 1/2 cups sugar and 1/4 cup flour, mixing until smooth.

Pour the passion fruit filling over the cooled shortbread crust, spreading evenly, and bake for 25-35 minutes until edges are set.

Let the bars cool on a wire rack for about an hour before refrigerating for at least an hour to firm up.

Cut into squares and dust with powdered sugar if desired. Serve chilled.