If you loved my sourdough lemon bars, you're going to fall hard for these sourdough lime bars. They're bright, tangy and unapologetically zesty, with the same buttery shortbread crust and silky custard filling, but with a sharper citrus edge that lime lovers will appreciate. These are the kind of sourdough dessert bars that feel cheerful, a little grown-up, and completely at home on a summer table or a winter dessert spread.
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This recipe is based on my reader-favourite sourdough lemon bars, but tweaked and rebalanced so lime can properly shine without overpowering the bake. Looking for more summery ideas? Head to our Summer Sourdough recipes!
Sourdough Discard In Crust And Filling
One of the reasons this recipe works so well is that sourdough discard is used in both elements: the shortcrust base and the lime filling.
In the crust, discard adds a little moisture and tenderness, helping create that melt-in-the-mouth, buttery shortbread texture without making the base heavy. The acidity also subtly sharpens the flavour, which works beautifully with citrus.
In the filling, sourdough discard blends seamlessly into the custard. Lime juice is already acidic, so the discard doesn't fight it. Instead, it deepens the tang and rounds out the sweetness, giving you a lively but balanced flavour. As a bonus, that acidity helps the bars keep well, which means these sourdough dessert bars stay fresh for longer than most.
Ingredient Notes
- Unsalted butter - Use good-quality butter for the shortbread base. Salted butter can throw off the balance.
- Powdered sugar (icing sugar) - Creates a fine, tender crumb in the crust rather than a gritty one.
- Sourdough discard (100% hydration) - Works in both crust and filling. Avoid discard with strong acidity or hooch.
- Vanilla bean paste - Optional, but softens the sharpness of lime nicely.
- Salt - A small amount sharpens flavour and prevents the bars tasting flat.
- Plain flour (purpose flour) - Keeps the base tender. You can replace 20 g with rice flour for extra crumble.
- Granulated sugar - Sweetens the filling and balances the lime juice.
- Lime zest - Use a microplane to avoid bitterness. Key limes work beautifully if you can get them.
- Eggs - Provide structure for the custard. Use large eggs at room temperature.
- Fresh lime juice - Always fresh. Bottled juice lacks brightness and complexity. Got extra limes? Make our 3-ingredient Lime Possets next!
- Powdered sugar for finishing - Dust just before serving for the cleanest look.
Step-By-Step Method
1. Preheat the oven to 180°C (350°F) and line a 20 × 20 cm baking tin with parchment paper, leaving overhang for easy lifting.
2. In a food processor, combine butter, powdered sugar, sourdough discard, vanilla, salt and flour. Pulse just until the flour mixture starts to clump.
3. Press the dough evenly into the bottom of the prepared pan, making sure it reaches the corners. Prick all over with a fork.
4. Bake for about 20-25 minutes, until lightly golden brown around the edges and set.
5. While the base bakes, rub lime zest into the granulated sugar in a large bowl until fragrant.
6. Whisk in the eggs, sourdough discard and lime juice gently until smooth and glossy. You may also add a drop of green food colouring if you wish.
7. Pour the lime curd filling over the hot base as soon as it comes out of the oven.
8. Return to the oven and bake for 22-24 minutes, until the centre has only a slight jiggle.
9. Cool at room temperature for about an hour, then chill for at least 3 hours, ideally overnight.
10. Lift out, slice into neat squares, and dust the top of the bars with powdered sugar just before serving.
Important Recipe Tips
- Use a microplane for lime zest - It extracts fragrant oils without digging into the bitter white pith.
- Rub zest into sugar first - This releases citrus oils and gives you a brighter, more even lime flavour.
- Don't over-whisk the filling - Too much air leads to bubbles, cracks and a rubbery custard.
- Watch bake times closely - Overbaking causes grainy filling and dull flavour.
- Chill fully before slicing - These bars need time to set for clean, sharp edges.
- Dust with powdered sugar at the last minute - Otherwise, it dissolves into the surface.
- Use a thin, sharp knife - Heat and wipe it between cuts for professional-looking slices.
Troubleshooting
Soggy base. Usually caused by underbaking. The crust should be lightly golden before adding the filling. For extra insurance, replace 20 g of flour with rice flour or cornflour.
Bars not setting / runny centre. Either underbaked or sliced too early. The centre should wobble slightly, not ripple. Chill thoroughly before cutting.
Grainy or rubbery filling. Eggs were overcooked or over-whisked. Mix gently and bake just until set.
Overly sour flavour. These are intentionally bright, but discard that smells sharp or has visible hooch will push things too far. Use fresh, mild discard.
Storage
Store sourdough lime bars in an airtight container in the fridge for up to 5 days. For longer storage, wrap tightly in plastic wrap and freeze for up to 2 months. Thaw overnight in the fridge and dust with confectioners' sugar just before serving.
More Sourdough Discard Recipes
If you enjoy turning excess starter into cheerful treats like these sourdough dessert bars, you'll find plenty more ways to use it in my sourdough discard recipe collection. Some of my favourite recipes to satisfy your sweet tooth are below:
Sourdough Lime Bars
Equipment
- 20 × 20 cm (8 × 8 in) Baking Tray
Ingredients
Shortcrust Pastry Base
- 150 g unsalted butter
- 65 g powdered sugar
- 50 g sourdough discard 100% hydration
- 1 teaspoon vanilla bean paste optional
- ½ teaspoon salt
- 210 g plain flour all purpose flour
Lime Filling
- 200 g granulated sugar
- 1 tablespoon lime zest finely grated
- 4 large eggs
- 50 g sourdough discard 100% hydration
- 120 g fresh lime juice
Instructions
- Preheat the oven to 180°C (350°F) and line a 20 × 20 cm (8 × 8 in) baking tin with high rims with parchment paper, leaving the sides overhanging the edges (it will make it possible to lift the lime bars out of the tin after baking).
- Add the butter, powdered sugar, vanilla, sourdough discard, flour, and salt to a food processor and mix just until it starts clumping together. Be careful not to overmix.
- Tip the pastry into the prepared baking tray and press it into an even layer using your fingers or the flat base of a glass/ mug.
- Prick the base all over with a fork, then bake for 20-25 minutes, until the edges are lightly golden and the shortcrust is baked through. TIP: Don't bake the base in advance and let it cool - the lime mixture needs to go on while the crust is still hot.
- Add the lime zest to the sugar and use your fingertips to work them together until the sugar turns lightly fragrant and slightly damp.
- Whisk in the eggs, sourdough discard and lime juice, mixing until the filling is smooth and glossy. You may add a drop of green food colouring, if you wish.
- Pour the lime mixture over the baked base as soon as it's out of the oven.
- Return to the oven and bake for 22-24 minutes, until the centre is just set and no longer jiggles when you gently shake the tin.
- Leave the bars to cool in the baking tin at room temperature for about an hour, then transfer to the fridge for at least 3 hours (ideally, overnight) until fully chilled.
- Lift out using the parchment paper, slice into neat squares and finish with a light dusting of icing sugar before serving. Decorate with candied citrus peel, thyme leaves or freeze-dried raspberries.
Nutrition
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