Ingredients

3/4 cup plain flour (all purpose flour)

1/4 cup rice flour (or cornstarch/cornflour)

1/2 cup icing sugar (powdered sugar, sifted)

1/4 tsp salt

110g / 1 stick unsalted butter (cold, cut into 1cm / 1/2″ cubes)

3 large eggs (55-60g / 2oz each)

1 cup caster sugar (super-fine sugar, can substitute regular sugar)

2 tbsp plain flour (all purpose flour)

1 tbsp lemon zest (do this before juicing)

1/2 cup lemon juice (from 2 – 3 lemons)

Instructions

Step 1: Preheat your oven to 180°C (350°F) or 160°C (320°F) if using a fan oven. Prepare a 20cm (8″) square baking tin by spraying it lightly with oil and lining it with baking or parchment paper, leaving an overhang for easy lifting after baking.

Step 2: For the base, combine the shortbread base ingredients (3/4 cup plain flour, 1/4 cup rice flour, 1/2 cup icing sugar, 1/4 tsp salt, and cold butter cubes) in a food processor fitted with an “S” blade. Pulse 5 to 10 times until the mixture resembles coarse sand. Alternatively, use your fingers to rub the butter into the flours until crumbly. Pour the mixture into the prepared pan and press firmly and evenly into the base and edges using the back of a spoon or a flat object.

Step 3: Bake the base for about 20 minutes or until the edges turn golden and the center is a pale gold color. Remove from the oven but do not cool before adding the topping.

Step 4: While the base bakes, whisk together the lemon curd ingredients in a bowl: 3 large eggs, 1 cup caster sugar, 2 tbsp plain flour, 1 tbsp lemon zest, and 1/2 cup lemon juice until smooth and well combined.

Step 5: Pour the lemon curd mixture over the hot shortbread base and return the pan to the oven. Bake for an additional 20 minutes, or until the topping is set but still slightly soft in the center.

Step 6: Remove from the oven and let cool at room temperature for 1 hour. Then chill in the refrigerator for at least 2 hours to fully set. Use the parchment overhang to lift the bars out of the tin, slice into 16 squares, dust with icing sugar, and serve.

Tips & Variations

For a gluten-free version, substitute the all-purpose flour with a gluten-free blend and ensure your rice flour or cornstarch is gluten-free.

Use freshly squeezed lemon juice for the best bright and fresh flavor.

Press the shortbread base evenly and firmly for a crisp, sturdy bottom layer that holds the lemon curd well.

Dust with additional lemon zest along with icing sugar for an extra citrusy aroma.

FAQs

Can I use regular sugar instead of caster sugar?

Yes, regular granulated sugar can be used if caster sugar is unavailable, though the texture may be slightly less smooth. For best results, pulse the sugar briefly in a food processor to make it finer before mixing.

Why is the lemon filling slightly soft after baking?

The lemon curd should be set but still soft to achieve a smooth and creamy texture. It will firm up further as it cools and chills in the refrigerator, ensuring a perfect balance between firm and silky.