These easy lemon bars (or lemon slices) consist of a delicious shortbread crust topped with a very more-ish lemon filling that will keep you coming back for more.
Preheat the oven to 180°C/350F. Grease and line a 9-inch square cake pan (23cm square) with parchment paper (making sure the baking paper hangs over the sides of the pan to allow for easy removal once the slice has cooled).
In a large bowl, add the softened butter, caster, icing sugar, and salt (if using unsalted butter). Cream using a whisk until soft and well-combined. (*Note 5)
¾ cup butter, ½ cup white granulated sugar, ½ cup icing sugar
Add in the flour and salt and mix with a spoon until a soft pliable dough is formed. Then knead the dough a few times by hand to ensure the dough is fully incorporated.
2 cups plain flour, ½ teaspoon table salt
Press the shortbread crust mixture into the prepared pan. Then use the back of a measuring cup and press the dough firmly into the pan. Prick the dough with a fork throughout and bake for 20 minutes until the base is just slightly golden brown.
While the base is baking, make the lemon bar filling. Place the sugar and lemon zest in a large mixing bowl, or the bowl of a stand mixer. Begin by rubbing the lemon zest into the sugar (*Note 6).
Then add in the flour, and mix through. Then add in the eggs and lemon juice. Beat together for 2-3 minutes.
4 eggs, 1¼ cups white granulated sugar, 4 tablespoons plain flour, zest of 2 lemons, ½ cup lemon juice
When the biscuit base is golden brown it is done. Then pour the lemon filling on top of the baked crust and bake for a further 20 minutes or until the middle just has the slightest jiggling.
Turn off the oven, and prop it open with a wooden spoon, allowing the lemon squares to cool slowly in the oven for an hour. Remove from the oven and allow to cool to room temperature before transferring to the fridge for at least 2 hours or overnight. (*Note 7)
Lift the slice out of the cake pan, and place it on a cutting board. Use a sharp clean knife for clean slices and cut into 20-25 squares. Decorate with a sprinkling of icing or powdered sugar.
All temperatures stated are for conventional ovens. Decrease the temperature by 20°C/25°F or gas mark 1 for "fan" or air-fryers.
Video
Notes
For butter: 1 cup of butter = 225 grams (which is 2 sticks of butter), and slightly less than a metric cup. Many slice recipes use melted butter, but I prefer the outcome when using softened butter.
I decreased the amount of sugar in my go-to lemon slice recipe for the topping from 300g to 250g. If you like things on the sweeter side, you can definitely up the sugar factor to 300g.
New Zealand size 6 eggs are around the same size as an Australian/South African Large or a US/Europe Medium.
Fresh lemons are a must for a good lemon bar. This recipe requires ½ cup (120mL) of lemon juice, which is approximately the amount of juice that can be squeezed out of two large lemons. If your lemons are small, then you may need an additional lemon or two. To zest a lemon you can use a zesting tool or a microplane/fine grater.
It can be quite cold in my kitchen (especially during winter) and sometimes I have to zap the butter in the microwave after the addition of the cold sugar to get it back to the correct soft texture.
The zest can be rubbed into the sugar using a stand mixer or electric mixer but beaten together for a minute or two at medium speed.
Allowing the lemon slice to cool slowly reduces the chances of the lemon filling cracking. However, a few cracks in the top do not take away how delicious these lemon bars are.
STORAGE AND FREEZING
This lemon slice can be stored in the fridge in an airtight container for up to a week, or frozen for up to 3 months. To freeze, slice into individual portions, then wrap in cling film/plastic wrap and aluminum foil before placing into an airtight container. To defrost, unwrap and allow the slice to thaw in the fridge before serving.