Homemade Lemon Rhubarb Bars Recipe

Lemon bars are already pretty great on their own, bright, tangy, and impossible to eat just one of. But add rhubarb to the filling and something genuinely special happens. Homemade lemon rhubarb bars feature a buttery shortbread crust topped with a tart, vibrantly pink lemon-rhubarb curd filling, dusted with icing sugar and sliced into clean, portable squares, the kind of springtime bake that disappears from a table faster than you’d expect. I brought these to a gathering once and left with an empty tray and three recipe requests.

Why Lemon and Rhubarb Work So Well Together

Both lemon and rhubarb are unapologetically tart. So why do they work together instead of cancelling each other out? Because sugar plays a different role with each one. With lemon, sugar softens the citrus’s sharpness into brightness. With rhubarb, sugar draws out the natural fruity flavour hiding underneath all that acidity. Combined, they create a filling that tastes layered and complex, tart upfront, fruity in the middle, and bright at the finish.

The rhubarb also brings something lemon curd alone can’t a beautiful natural pink colour that sets the filling apart visually. No food colouring needed. Just good rhubarb, cooked down properly, doing exactly what it’s supposed to do.

Ingredients You’ll Need

Two distinct components a shortbread base and a lemon rhubarb curd. Neither is complicated, and both come together quickly.

For the shortbread crust

• 200g plain flour
• 60g icing sugar
• ¼ tsp salt
• 170g unsalted butter, cold and cubed
• 1 tsp vanilla extract

For the lemon rhubarb filling

• 300g fresh rhubarb, trimmed and roughly chopped
• 200g caster sugar, divided
• 3 large eggs plus 2 egg yolks
• 80ml fresh lemon juice (about 2–3 lemons)
• 1 tbsp lemon zest
• 3 tbsp plain flour
• Pinch of salt
• Icing sugar for dusting to finish

FYI use the reddest rhubarb stalks you can find. The deeper the red colour of the raw rhubarb, the more vibrant the pink your filling will be. Pale green rhubarb still tastes great but produces a much duller, greener filling that loses the visual wow factor entirely.

How to Make It Step by Step

Step 1: Make and pre-bake the shortbread crust

Preheat your oven to 180°C (160°C fan). Line a 20x30cm baking tin with parchment, leaving overhang on the sides for easy lifting. Pulse the flour, icing sugar, and salt together, then add the cold cubed butter and vanilla. Mix until the dough resembles coarse crumbs and just comes together when pressed. Press firmly and evenly into the base of the lined tin and bake for 18–20 minutes until lightly golden. Don’t skip the pre-bake a raw crust under a wet filling stays soggy and never crisps up properly.

Step 2: Cook down the rhubarb

While the crust bakes, place the chopped rhubarb in a small saucepan with 50g of the caster sugar and 2 tablespoons of water. Cook over medium heat, stirring occasionally, for 8–10 minutes until the rhubarb breaks down completely into a soft, bright pink compote. Push through a fine mesh sieve to remove any fibrous bits and measure out 120ml of smooth rhubarb purée. This step concentrates the flavour and removes the stringy texture that would otherwise ruin the filling’s smoothness.

Step 3: Make the lemon rhubarb filling

Whisk together the eggs, egg yolks, remaining 150g caster sugar, lemon juice, lemon zest, flour, and salt until fully combined and smooth. Stir in the rhubarb purée; the mixture will turn a beautiful rosy pink. Pour directly over the hot pre-baked crust straight from the oven. The hot crust helps set the filling base quickly and creates a cleaner boundary between layers.

Step 4: Bake, cool, and cut

Return to the oven and bake for a further 22–25 minutes until the filling is set at the edges but still has a very slight wobble in the centre, it firms up as it cools. Cool completely in the tin at room temperature, then refrigerate for at least 2 hours before cutting. IMO, overnight chilling gives the cleanest cuts and the most defined layers. Dust generously with icing sugar just before serving.

Tips for Getting Them Perfect

• Use cold butter in the crust. Room-temperature butter makes the shortbread greasy and tough rather than crumbly and tender
• Strain the rhubarb purée thoroughly, as any fibrous bits in the filling create an unpleasant texture in an otherwise silky curd
• Pour the filling onto a hot crust, not a cooled one. The temperature difference helps the layers bond cleanly
• Dust with icing sugar right before serving, not before refrigerating, so it dissolves and disappears in the fridge overnight
• Use a sharp knife wiped clean between each cut for the neatest, most professional-looking bars

Common Questions

Can I use frozen rhubarb for this recipe?

Yes, frozen rhubarb works well in the cooked purée step. Thaw it completely and drain off any excess liquid first; otherwise, the purée comes out too watery, and the filling won’t set properly. The flavour is very similar to fresh, though the colour is sometimes slightly less vivid.

How do I store lemon rhubarb bars?

Store them in an airtight container in the fridge for up to 4 days. The shortbread base softens slightly by day three, but the flavour actually deepens and improves. Keep them refrigerated; the egg-based filling doesn’t hold safely at room temperature for extended periods.

Can I make these bars ahead of time?

Absolutely, and they’re actually better made the day before. The filling sets more firmly overnight and the flavours meld together in a way that freshly baked bars simply don’t achieve. Add the icing sugar dusting on the day of serving so it stays visible and doesn’t dissolve into the filling.

Final Thought

Lemon rhubarb bars hit that sweet spot between effort and reward that makes baking genuinely satisfying. One pre-baked crust, one cooked purée, one poured filling, and you end up with something that looks beautiful, travels well, and tastes like spring in every bite.

Make them at the start of rhubarb season when the stalks are reddest, and the flavour is at its sharpest. Cut them into generous squares, dust them with icing sugar right before serving, and watch them vanish. That’s the best possible outcome for any bake.