Mary Berry Lemon Rhubarb Sourdough Discard Cake Recipe

This soft and tender lemon rhubarb sourdough discard cake is a brilliant way to use up sourdough discard. It has a light, airy crumb with juicy bursts of rhubarb in every bite, balanced by fresh lemon zest and a touch of honey. Despite using discard, the flavour is clean and bright—no sourness at all.

Perfect for dessert, afternoon tea, or even breakfast, this cake is simple to make and wonderfully versatile.

---

What is Lemon Rhubarb Sourdough Discard Cake?

This cake is a lightly sweetened, fruit-filled bake that incorporates sourdough discard into the batter. The discard improves texture, creating a fluffy yet moist crumb while enhancing the natural flavours of lemon and rhubarb. It’s an easy, no-waste recipe that turns leftover starter into something truly delicious.

---

Why You’ll Love This Recipe

• Light and fluffy texture – Soft crumb with a delicate structure
• No sour taste – The discard enhances flavour without overpowering
• Great way to reduce waste – Perfect use for leftover sourdough starter
• Bright, fresh flavour – Lemon and rhubarb complement each other beautifully
• Versatile – Enjoy as dessert, snack, or breakfast

---

Ingredients You’ll Need

• 8 oz fresh rhubarb (cut into chunks, plus extra for topping)
• 170g all-purpose flour
• 1½ tsp baking powder
• ½ tsp fine salt
• 155g cane sugar (plus extra for topping)
• ½ cup neutral oil (sunflower or grapeseed)
• 2 tsp lemon zest
• 2 large eggs (room temperature)
• 2½ tbsp honey
• 65g sourdough discard (room temperature preferred)
• 1½ tsp vanilla extract
• 1 tbsp fresh lemon juice
• 2½ tbsp milk

---

Kitchen Equipment

• 8-inch or 9-inch square cake pan
• Mixing bowls
• Hand or stand mixer
• Spatula
• Cooling rack

---

Step-by-Step Instructions

Step 1: Prepare the oven and pan

Preheat your oven to 175°C (350°F). Grease and line a square cake pan with baking paper.

Step 2: Prep the rhubarb

Place chopped rhubarb into a bowl. Toss it with a couple of teaspoons of the flour mixture (this helps stop it from sinking). Set aside.

Step 3: Mix dry ingredients

In a separate bowl, whisk together the flour, baking powder, and salt.

Step 4: Cream oil and sugar

In a large bowl, beat the sugar, oil, and lemon zest together for about 1 minute until slightly thickened and fragrant.

Step 5: Add wet ingredients

Mix in the eggs and beat until the mixture looks light and slightly frothy. Add honey, sourdough discard, vanilla extract, lemon juice, and milk. Mix until just combined.

Step 6: Combine batter

Add the dry ingredients and mix on low speed until no dry flour remains. Do not overmix.

Step 7: Fold in rhubarb

Gently fold the coated rhubarb into the batter. Pour the mixture into the prepared pan and smooth the top.

Step 8: Decorate

Arrange the remaining rhubarb pieces on top in a pattern if desired. Sprinkle a little extra sugar over the surface.

Step 9: Bake

• For an 8-inch pan: Bake for 25 minutes, then reduce heat to 165°C (330°F) and bake for another 15 minutes.
• For a 9-inch pan: Bake for 20 minutes, then reduce heat and bake for an additional 8–10 minutes.

The cake is ready when a toothpick inserted comes out with a few moist crumbs.

Step 10: Cool and serve

Allow the cake to cool in the pan before transferring to a rack. Slice and serve once cooled.

---

Common Mistakes (And How to Fix Them)

• Cake too dense – Avoid overmixing once flour is added
• Rhubarb sinks – Toss it lightly in flour before folding in
• Dry texture – Be careful not to overbake
• Too sour flavour – Use fresher sourdough discard

---

Healthier Swaps

• Replace some oil with unsweetened yogurt
• Reduce sugar slightly if rhubarb is mild
• Use wholemeal flour for added fibre (texture will be denser)

---

Ingredient Substitutions

• Honey → Maple syrup or extra sugar
• Milk → Any plant-based milk
• Oil → Melted butter
• Rhubarb → Try berries for a different twist

---

Serving Ideas

• Serve with whipped cream
• Add a scoop of vanilla ice cream
• Enjoy with Greek yogurt for breakfast
• Pair with tea or coffee

---

Expert Tips

• Use room temperature ingredients for best texture
• Don’t skip the lemon zest—it adds essential flavour
• Bake just until done to keep the crumb soft
• Let it cool slightly before slicing for clean cuts

---

Storage Instructions

• Store in an airtight container in the fridge for up to 4 days
• Bring to room temperature before serving, or enjoy chilled

---

Freezing Instructions

• Slice and wrap individually
• Freeze for up to 2 months
• Thaw overnight in the fridge or at room temperature

---

Nutritional Information (per serving, approx.)

• Calories: ~280 kcal
• Carbohydrates: 35g
• Protein: 5g
• Fat: 13g
• Sugar: 18g

---

FAQ

What does sourdough discard do in this cake?

Sourdough discard helps create a soft, tender crumb by increasing the acidity of the batter, which weakens gluten. This results in a lighter, fluffier texture without making the cake taste sour.

Will the cake taste sour from the sourdough discard?

No, the flavour is not sour. Instead, the discard enhances the overall taste and allows the lemon, honey, and rhubarb to stand out more clearly.

How fresh should sourdough discard be for baking?

For best results, use discard that is less than 5 days old. Older discard can develop a stronger tang, which may slightly affect the flavour.

Can I use frozen rhubarb instead of fresh?

Yes, frozen rhubarb works well. Thaw and drain it first to remove excess moisture so the cake doesn’t become too wet.

Why coat the rhubarb in flour before adding it to the batter?

Lightly coating the rhubarb helps prevent it from sinking to the bottom during baking, ensuring an even distribution throughout the cake.

Can I make this cake without honey?

Yes, you can substitute honey with maple syrup or an equal amount of sugar. Keep in mind this may slightly change the flavour and moisture.

How do I know when the cake is done baking?

Insert a toothpick into the centre—if it comes out with a few moist crumbs (but no wet batter), the cake is ready.

How should I store this cake?

Store the cake in an airtight container in the refrigerator for up to 4 days. It stays moist and can be enjoyed chilled or at room temperature.

Can I freeze sourdough rhubarb cake?

Yes, wrap slices tightly and freeze for up to 2 months. Thaw overnight in the fridge or at room temperature before serving.

What’s the best way to serve this cake?

It’s delicious on its own, but even better served with whipped cream, yogurt, or a scoop of vanilla ice cream for dessert.

---

Other Similar Recipes

• Mary Berry Strawberry Rhubarb Jam Recipe
• Mary Berry Gluten-Free Rhubarb Crisp Recipe
• Mary Berry Rhubarb and Ginger Jam Recipe

---