This baked lemon slice is the classic tea-and-a-chat recipe your nan probably made, minus the fuss.
It's light, tangy and ready in under an hour, right alongside my Lemon Coconut Slice and Lemon & Yoghurt Loaf as one of my most-made lemon bakes.
A Quick Look At The Recipe
✅ Recipe Name: Baked Lemon Slice with Lemon Frosting
🕒 Ready In: 10 minutes prep + 20 minutes baking + cooling
👪 Serves: 16 pieces
🍚 Calories: 238kcal per piece
🥣 Main Ingredients: butter, caster sugar, lemon, flour
📖 Dietary Info: freezer-friendly, easily doubled
⭐ Why You'll Love It: a light, one-bowl slice with a proper tangy lemon frosting, no fancy ingredients needed.
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Wow, what a beautiful cake, light and very lemony, just as a lemon slice should be. We made two, both for sharing, and everyone agreed this was a recipe to keep.
- Nici
This is one of those slices that disappears fast at morning tea. If you're on a lemon kick, try my Gluten Free Lemon Cake or No-Bake Lemon Cheesecake next, or grab a jar of lemons and go all in with my Individual Lemon Puddings.
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Why You're Going To Love This Recipe
- One bowl, 30 minutes - mix, bake, ice. That's genuinely it.
- Made from basic pantry and fridge staples, so there's no special shopping trip needed.
- Freezer-friendly, perfect for stocking the lunchbox stash ahead of time.
- Nearly 100 five-star reviews and counting. This one's a proven classic, not just a pretty photo.
Slice Ingredients
Nothing fancy here, just a couple of things worth getting right.
Note: Scroll to the recipe card at the bottom for the ingredient quantities and full detailed method.
- Fresh lemon juice and zest - bottled juice works in a pinch, but fresh gives you a much brighter, more lemony slice. Zest before you juice, it's much easier that way round.
- Pure icing sugar (not icing sugar mixture) for the frosting. It sets firmer, which matters if this slice is heading into a lunchbox.
Variations
- Add coconut: stir ½ cup of desiccated coconut through the batter for a coconutty twist, or make my Lemon Coconut Slice instead.
- Swap the lemon for orange zest and juice for a milder, sweeter version.
- Double it: this recipe doubles easily in a slightly larger tin if you're feeding a crowd; just add a few extra minutes to the bake time.
- Skip the frosting and dust with icing sugar instead for a lighter, less sweet finish.
How To Make Baked Lemon Slice
Four easy steps and you're done.
Note: Scroll to the recipe card at the bottom for the ingredient quantities and full detailed method.
- Step 1: Beat the base. Preheat the oven to 170°C fan-forced and line a 20cm square tin. Beat the butter, caster sugar and lemon zest until smooth and creamy.
- Step 2: Add the wet ingredients. Add the eggs and lemon juice and beat well to combine.
- Step 3: Fold through the dry ingredients. Gently fold through the baking powder and flour, then spread into the prepared tin and bake for 20-25 minutes, or until a skewer comes out clean.
- Step 4: Make the frosting and ice. Whisk together the sifted icing sugar, butter and lemon juice until smooth. Once the slice is completely cool, spread the frosting over the top and let it set.
Recipe Tips
- Stick to a 20cm x 20cm tin. A bigger tin spreads the mixture thinner and you'll lose that lovely soft thickness.
- For neat, clean squares, warm your knife under hot water and wipe it dry between cuts.
- Storage: keep it in an airtight container at room temperature for up to 5 days so it stays soft and moist.
- Freezing: wrap well and freeze for up to 1 month. Thaw at room temperature before serving.
- Frosting too thick or thin? A splash more lemon juice loosens it, a spoon of extra sifted icing sugar firms it back up.
Baked Lemon Slice FAQs
This almost always comes down to baking powder that's past its best, it's what gives the batter its lift. Double-check the date on the tin and grab a fresh one if you're not sure. Using a tin bigger than 20cm x 20cm will also spread the mixture thinner.
Yes, it's a great make-ahead slice. Bake and ice it the day before, store it in the fridge overnight, then bring it back to room temperature before serving.
Keep it in an airtight container at room temperature for up to 5 days. To freeze, wrap it well (iced or plain) and freeze for up to 1 month, then thaw at room temperature.
You can, and it'll still work, but fresh lemon juice and zest give a much brighter, more lemony flavour. If you've got fresh lemons on hand, use them.
All my recipes are written for fan-forced ovens. For a conventional oven, bump the temperature up by 10-20 degrees and keep an eye on it near the end so it doesn't brown too fast.
More Lemon Recipes You'll Love
Got a fruit bowl full of lemons? Here's a few more ways to use them up:
Baked Lemon Slice
Ingredients
- 115 g butter softened to room temperature
- 150 g (¾ cup) caster sugar
- lemon zest from 1 lemon
- 2 eggs room temperature
- lemon juice from 1 lemon
- ½ teaspoon baking powder
- 95 g (¾ cup) plain flour
For the frosting
- 270 g (1 ¾ cup) pure icing sugar sifted, see notes
- 65 g butter softened to room temperature
- 4 tbs lemon juice (extra if needed)
Instructions
Conventional Method
- Preheat oven to 170 degrees celsius (fan-forced). Grease and line a 20cm x 20cm cake tin with baking paper. Set aside.
- Place the butter, caster sugar and lemon zest into a large bowl. Beat until smooth and creamy.
- Add the eggs and lemon juice and beat to combine.
- Fold through the baking powder and flour.
- Spoon the mixture into the prepared tin and bake for 20-25 minutes or until a skewer inserted into the middle comes out clean.
- To prepare the frosting, place the sifted icing sugar, butter and lemon juice into a bowl. Whisk until smooth and creamy. If the frosting is a little too thick, add a bit more lemon juice and whisk again. If too thin, add a little more icing sugar.
- Spread the frosting over the cooled slice and allow to set.
Thermomix Method
- Preheat oven to 170 degrees celsius (fan-forced). Grease and line a 20cm x 20cm cake tin with baking paper. Set aside.
- Place the butter, caster sugar and lemon zest into the Thermomix bowl. Insert the butterfly and mix for 30 seconds, Speed 4. Scrape down the sides of the bowl and repeat until smooth and creamy.
- Add the eggs and lemon juice and mix for 10 seconds, Speed 4, to combine. Remove the butterfly.
- Add the baking powder and flour and mix for 10 seconds, Speed 4. Scrape down the sides and repeat for a further 5 seconds.
- Spoon the mixture into the prepared tin and bake for 20-25 minutes or until a skewer inserted into the middle comes out clean.
- To prepare the frosting, place the icing sugar, butter and lemon juice into the Thermomix bowl and mix for 20 seconds on Speed 4. Scrape down the sides of the bowl with a spatula. Mix for an extra 30 seconds, Speed 4.
- If the frosting is a little too thick, add a bit more lemon juice and whisk again. If too thin, add a little more icing sugar.
- Spread the frosting over the cooled slice and allow to set.
Notes
- Use pure icing sugar (as compared to icing sugar mixture) as it will set the frosting firmer than icing sugar mixture. A firmer icing is best when sending the slice in school lunch boxes.
- If your frosting is too thick to spread, add a small amount of extra lemon juice and mix again.
- If your frosting is too thin, add some extra sifted icing sugar.
- Storing & Freezing - store this slice in an airtight container for up to 5 days, or wrap well and freeze for up to 1 month. Allow to thaw before consuming.
Rachel says
Hi I've just made this and found that when I put the eggs and lemon juice into the creamed butter and sugar it separated and curdled. Did I do something wrong? It's in the oven so fingers crossed it will come out OK.
Lucy Mathieson says
Hi Rachel, it should be absolutely fine. It would have just been that the eggs were not at room temp. xx
Clytie says
How much is the juice of one lemon? Quantity varies enormously, as it does with oranges. Then we have pulp of 3 passion fruit???? Your help would be appreciated.
Lucy Mathieson says
Generally the juice of 1 lemon is about 3 tbs. I would adjust the amount of lemon you use in this recipe depending on your tastes. Personally I love lemon and so always add a little extra! xx
mel @ C says
i would really love to bake using oil. plz help
Lucy Mathieson says
Hi Mel, I've only ever made this with butter - sorry!
Nikky says
Yum! Perfect way to use up some of the crop from our hugely prolific lemon tree. Just one question: butter is so terribly expensive over here in NZ at the mo, do you have any experience of replacing butter with oil? I don't want to damage the flavour or texture!
Lucy Mathieson says
Hi Nikky, hmm I personally haven't tried it with oil and don't think it would have the same texture or flavour. You could try though!! I didn't realise butter was expensive in NZ!!!
Nikky says
Thanks Lucy. It's nearly doubled in price in the last year! 🙁
Lucy Mathieson says
Wow I didn't realise!!!
Nicoletta says
Same here in qld. Was paying 1.39 approx. 12 months ago and now 2.65 for 250g.
Swah says
Oh yum, lemon slice is one of my favourite childhood treats. This looks divine!.
Lucy Mathieson says
Mine too!
Liz says
Butterfly used and on Speed 6? Isn't the max speed when butterfly is called for is speed 4?
Lucy Mathieson says
My apologies Liz, yes that was a typo (I've fixed it now). It should have been Speed 4. Thanks for picking it up! xx