This easy lemon slice recipe consists of a delicious shortbread crust that is topped with a tangy lemon curd filling and finished with a sprinkling of powdered sugar.
This baked lemon slice (or lemon bar or lemon squares) comes together fairly quickly, from fairly simple ingredients. This recipe used fresh lemon juice and zest for that ultimate tangy flavor.
These easy, homemade lemon squares are perfect for any occasion. Such as Mother's Day or Father's Day, or a simple family barbecue or get-together.
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Recipe Development
For this recipe, I started with the shortbread base that I have used and tweaked in my millionaire's shortbread, jam squares, and tan slice recipes.
And then I had to play around with the lemon curd filling. In my first test, I used 300 grams of sugar. And while I was happy with the results I reduced the sugar to 250 grams. And was super happy with those results.
Along with testing comes the freezer test. And this lemon slice freezes and defrosts well. This makes a great make-ahead dessert, as you can freeze the slice for up to 3 months!
Ingredient Notes & Substitutions
Here are notes on the ingredients used, please refer to the recipe card for full quantities and detailed steps.
- Butter adds flavor, softness, and texture to the shortbread base. I use New Zealand butter which has around 82% butterfat, which is similar to a European or Irish butter. Butter can be substituted with a baking margarine.
- Plain flour (all-purpose flour/standard-grade flour) is used for the shortbread biscuit base, and in the lemon curd filling to help it thicken when it bakes.
- White sugar adds sweetness and moisture to the biscuit base and is used to sweeten the curd filling without competing with the lemon flavor.
- Icing sugar (powdered or confectioners' sugar) is a finely ground sugar that typically contains between 2 and 5% starch (such as tapioca or corn). This is used in the shortbread base to add a bit of snappiness, and then for decorating the lemon bars.
- Fresh lemon juice and fresh lemon zest flavor the curd. The juice of two lemons is approximately ½ cup or 120mL, however, if your lemons are small you may need an additional lemon or two to get to 120mL.
- Eggs - I use a New Zealand size 6 egg, which is an Aus/SA large, and an Euro/US medium.
- Salt is a crucial ingredient in all baked goods. I use table salt in all my recipes. One teaspoon of table salt equals 1.5 teaspoons of Morton Kosher Salt equals 2 teaspoons of Diamond Crystal.
Step-by-Step Instructions
Step 1 - 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).
Step 2- 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.
Top Tip - if your butter is feeling a bit hard, you can pop it into the microwave for short 10-20 second bursts to soften it up.
Step 3 - 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.
Step 4 - 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 20-25 minutes until the base is just slightly golden brown.
Step 5 - While the base is baking, make the lemon curd filling. Place the sugar and lemon zest in a large mixing bowl, or the bowl of a stand mixer. Rub the zest into the sugar.
Top Tip - if using a stand mixer or electric mixer, you can just beat the sugar and zest together on a low-medium speed instead of rubbing it in by hand.
Step 6 - Then add in the flour, and mix through. Then add in the eggs and lemon juice. Beat together for 2-3 minutes.
Step 7 - 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 20-25 minutes or until the middle just has the slightest jiggling.
Step 8 - 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 - allowing the lemon slice to cool slowly reduces the changes of the lemon filling cracking. But, a few cracks in the top do not take away how delicious these lemon bars are.
Step 9 - 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 generous dusting of icing or powdered sugar.
Expert Tips for This Recipe
- An oven takes about 15 to 20 minutes to preheat.
- If using a fan-assisted, convection or air-fryer, reduce the temperature by 20°C/25°F
- Remember that all ovens work slightly differently and bake times may need to be adjusted for your specific oven.
- I recommend using an oven thermometer for increased accuracy.
- Rubbing the zest into the sugar releases the oils and flavor from the zest, making sure these lemon bars are really nice and lemony.
- A metal pan heats up and cools down quicker than glass, and I prefer baking with metal pans.
- For really nice sharp edges, use a sharp knife and wipe down the blade between slices.
- Let the slice cool down completely before slicing and serving!
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.
Lemon Bars/Lemon Slice FAQ
To get clean even slices, mark your slice using a ruler, and then warm up your sharp knife in hot water, wipe dry, and cut. By warming up the blade and wiping it clean in between each slice you will get perfect slices.
The lemon slice should be cut once the lemon slice has been allowed to cool and set in the fridge for at least two hours.
Lemon bars can be stored in the fridge for up to a week, or up to 3 months when frozen.
Yes! These lemon bars are best made the day before and allowed to chill in the fridge overnight. However, the slice can also be made and frozen a few months (3 months) ahead of an event.
