Zesty Lemon Crumb Bars: A Sun-Drenched Treat.

Lemon Crumb Bars are the perfect intersection of a shortbread cookie and a tart lemon curd. Unlike traditional lemon bars that feature a smooth, custard-like top, crumb bars utilize a versatile “double-duty” dough that serves as both the buttery base and the golden, pebbled topping. This architectural choice provides a much-needed crunch to balance the silky, citrus-heavy center.

The success of this recipe lies in the balance of acidity. By using fresh lemon juice and a generous amount of zest, the filling remains bright and sharp, cutting through the richness of the butter-laden crust.¹ It is an honest, reliable dessert that travels well and offers a sophisticated, sunshine-bright flavor profile.

Ingredients

The Crust & Crumb Topping

250g All-Purpose Flour.
150g Granulated Sugar.
1/2 Teaspoon Baking Powder.
1/4 Teaspoon Salt.
225g Cold Unsalted Butter: Cubed.
1 Large Egg.
1 Teaspoon Vanilla Extract.

The Lemon Filling

300g Granulated Sugar.
2 Large Lemons: Zested and juiced (approx. 80ml juice).
1 Tablespoon Cornstarch.
1 Large Egg.
1/2 Teaspoon Vanilla Extract.

Instructions

1. Prep the Base

Preheat your oven to 190°C. Line a 20cm x 20cm (8×8 inch) baking pan with parchment paper, leaving an overhang on the sides for easy removal.

2. Create the Dough

In a large bowl, whisk together the flour, 150g sugar, baking powder, and salt. Use a pastry cutter or two forks to cut in the cold butter until the mixture resembles coarse crumbs. Stir in the egg and vanilla until a shaggy dough forms.

3. Press and Set

Divide the dough in half. Press one half firmly into the bottom of the prepared pan to create an even base. Place the remaining dough in the refrigerator to keep the butter cold.

4. Mix the Lemon Filling

In a separate bowl, whisk together the 300g sugar, lemon juice, lemon zest, cornstarch, egg, and vanilla. Whisk until the sugar has mostly dissolved and the mixture is smooth.

5. Assemble and Bake

Pour the lemon filling over the unbaked bottom crust. Retrieve the remaining dough from the fridge and crumble it evenly over the top of the lemon layer using your fingers.

6. The Bake

Bake for 35 to 40 minutes, or until the top is light golden brown and the lemon filling is set (it should only have a slight jiggle in the center).

7. Cool and Slice

This is the most important step: let the bars cool completely in the pan at room temperature, then refrigerate for at least 2 hours before slicing. This ensures the lemon layer sets into a firm, sliceable fudge rather than a liquid.

Flavor & Texture Notes

The primary sensation of these bars is vibrant contrast. The crust and crumble provide a salty-sweet, buttery crunch that shatters pleasantly, while the lemon center is intensely tart and velvety.

The lemon zest provides a floral, aromatic lift that prevents the sugar from feeling overpowering. It is a dense, satisfying dessert that feels both rustic and refined.

Tips & Variations

The Berry Twist: Scatter 100g of fresh blueberries or raspberries over the lemon filling before adding the crumb topping for a “Blueberry Lemon” version.
Almond Extraction: Add 1/2 teaspoon of almond extract to the crust dough for a nutty, professional bakery aroma.²
Glaze Finish: For extra sweetness, whisk together 60g powdered sugar with 1 tablespoon of lemon juice and drizzle it over the bars once they are completely cooled.³

Storage & Make-Ahead

Refrigeration: These bars contain egg and fruit juice, so they should be stored in an airtight container in the refrigerator. They stay fresh for up to 5 days.
Serving: While they can be eaten at room temperature, they are most refreshing when served slightly chilled.
Freezing: These bars freeze beautifully. Wrap individual squares in plastic wrap and store in a freezer bag for up to 3 months. Thaw in the fridge overnight.

FAQ

Why is my lemon layer runny?

This usually means the bars weren’t baked long enough or weren’t allowed to cool properly. The cornstarch needs heat to activate its thickening power, and the filling needs a cold environment to fully solidify.

Can I use bottled lemon juice?

I strongly advise against it. Fresh lemon juice provides the necessary acidity and brightness; bottled juice often has a metallic or dull aftertaste that can ruin the delicate flavor of the bars.

Can I use a larger pan?

If you use a 9×13 inch pan, you must double the recipe. If you don’t double it, the layers will be too thin and will likely burn before they set.

Conclusion

Lemon Crumb Bars are a masterclass in the “one-dough” technique. By utilizing the same mixture for the base and the topping, you minimize prep work while maximizing textural interest. It is a foolproof recipe that consistently delivers a bright, citrusy punch and a comforting, buttery finish.