Preheat the oven to 350 degrees.

Prepare an eight-by-eight-inch baking dish by lining it with parchment paper, leaving some hanging over the sides to help you remove the bars later.

In a large mixing bowl, beat the butter and sugars until the mixture is fluffy.

Add in the eggs, beating between each one, then beat in the salt, baking powder, zest and lemon curd.

Finally, beat in the flour until everything is just combined, and spread the batter evenly into the prepared baking dish.

Bake for 30 minutes or until the edges are browned.

Let the bars cool completely in the pan, and then use the parchment to remove and slice them. If you want to make them look a little fancier, lightly sprinkle the tops of the bars with some powdered sugar. Store the bars in an airtight container.