Preheat oven to 350 degrees F. Line a 8″ x 8″ pan parchment or non-stick foil with an overhang to lift it out.

Combine the butter, flour, powdered sugar, and salt in a medium bowl. Mix with a large spoon or your fingers until well combined. Let the warmth of your hand help to incorporate the butter with the flower and sugar. Press the dough evenly into your prepared pan.

Bake for 15 to 20 minutes, or until set and just beginning to turn color.

Add a cup to a cup and a half of the strawberry rhubarb curd on top and return the pan back to the oven and bake for another 18 to 20 minutes, or until lightly browned on top and no longer jiggling in the center.

Allow it to completely cool before serving. Remove the shortbread from the pan, sprinkle with powdered sugar, and cut into squares.