Can I use active sourdough starter instead of discard?

Yes, you can, but discard is often preferred for its more pronounced tang in recipes like this where it's not the primary leavener. If using active starter, the flavor might be milder. The recipe relies on baking powder/soda for lift.

Can I use frozen rhubarb for this sourdough cake?

Yes. Do not thaw completely. Toss the frozen, diced rhubarb with a tablespoon of all-purpose flour before adding it to the-batter to help absorb excess moisture. You might need to add a few extra minutes to the baking time.

How do I know when the coffee cake is done?

The top will be golden brown, and a toothpick inserted into the cake portion (avoiding rhubarb) should come out clean or with a few moist crumbs attached. The internal-temperature should be around 200-205°F (93-96°C).

My sourdough discard is very runny/thick. Does it matter?

This recipe is fairly forgiving. Standard discard (often 100% hydration, meaning equal parts flour and water by weight) works best. If your discard is extremely runny, the batter might be slightly wetter; if very thick, slightly drier. Minor variations are usually fine.

Why is my sourdough rhubarb bread/cake dense?

For this coffee cake, denseness could be due to overmixing the batter, using too much liquid, not enough leavening (baking powder/soda), or the oven temperature being too low. Ensure your leaveners are fresh!

Sourdough Rhubarb Streusel Coffee Cake Recipe

Description

A delicious and easy coffee cake featuring tangy rhubarb, a moist sourdough discard cake base, and a buttery cinnamon streusel topping. The perfect way to use up sourdough discard and celebrate spring flavors!

Ingredients

For the Rhubarb Layer:

3 cups 300-350g fresh rhubarb, washed and diced into ½-inch pieces
2 tablespoons granulated sugar
1 teaspoon orange zest ((optional))

For the Sourdough Streusel Topping:

¾ cup 90g all-purpose flour
½ cup 100g light brown sugar, packed
1 ½ teaspoons ground cinnamon
¼ teaspoon ground ginger or cardamom ((optional))
6 tablespoons 85g unsalted butter, cold and cubed
2 tablespoons sourdough discard ((unfed))
½ cup chopped pecans or walnuts ((optional))

For the Sourdough Cake Batter:

1 ¾ cups 210g all-purpose flour
1 ½ teaspoons baking powder
½ teaspoon baking soda
½ teaspoon salt
½ cup 113g unsalted butter, softened to room temperature
¾ cup 150g granulated sugar
2 large eggs (at room temperature)
1 cup 220-240g sourdough discard, (unfed), room temperature
1 ½ teaspoons vanilla extract
¼ cup 60ml milk or buttermilk, at room temperature

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Instructions

Prepare Rhubarb & Preheat Oven:
Preheat oven to 375°F (190°C). Grease and flour your 9×9 inch baking pan, or line with parchment paper, leaving an overhang.
In a medium bowl, combine the diced rhubarb, 2 tablespoons of granulated sugar, and optional orange zest. Toss gently and set aside.
Make the Sourdough Streusel Topping:
In a separate medium bowl, whisk together the ¾ cup all-purpose flour, ½ cup light brown sugar, 1 ½ tsp cinnamon, and optional ginger/cardamom for the streusel.
Add the 6 tbsp cold, cubed butter and 2 tbsp sourdough discard. Using your fingertips or a pastry blender, cut the butter and discard into the dry ingredients until the mixture resembles coarse crumbs.
If using, stir in the ½ cup chopped nuts. Place the streusel mixture in the refrigerator.
Prepare the Cake Batter:
In another medium bowl, whisk together the 1 ¾ cups all-purpose flour, 1 ½ tsp baking powder, ½ tsp baking soda, and ½ tsp salt. Set aside.
In a large bowl, using an electric mixer, cream the ½ cup softened butter and ¾ cup granulated sugar together until light and fluffy (about 2-3 minutes).
Beat in the 2 large eggs one at a time, mixing well after each. Scrape down the sides of the bowl.
Stir in the 1 cup sourdough discard and 1 ½ tsp vanilla extract until just combined.
Add half of the dry ingredient mixture to the wet ingredients and mix on low speed until just barely combined. Pour in the ¼ cup milk/buttermilk and mix on low. Add the remaining dry ingredients and mix on low speed only until no dry streaks of flour remain. Do not overmix.
Assemble and Bake:
Spread half of the cake batter evenly into the prepared baking pan.
Drain any excess liquid from the macerated rhubarb. Evenly distribute the rhubarb pieces over the batter.
Spoon or gently spread the remaining cake batter over the rhubarb layer.
Evenly sprinkle the chilled streusel topping over the batter.
Bake for 45-55 minutes, or until a toothpick inserted into the center of the cake portion comes out clean or with a few moist crumbs. The top should be golden brown. (If streusel browns too quickly, loosely tent with foil for the last 10-15 mins).
Cool and Serve:
Let the coffee cake cool in the pan on a wire rack for at least 20-30 minutes before slicing and serving.
Serve warm or at room temperature.

Notes

Room Temperature Ingredients: Ensure eggs, butter, sourdough discard, and milk are at room temperature for the best cake texture.
Do Not Overmix: Mix batter only until ingredients are just combined to prevent a tough cake.
Frozen Rhubarb: If using frozen rhubarb, do not thaw completely. Toss diced frozen rhubarb with 1 tablespoon of all-purpose flour before adding to the batter. Baking time may increase slightly.
Storage: Store in an airtight container at room temperature for up to 3 days, or refrigerated for up to 5 days. Freezes well for up to 3 months; wrap tightly.

Prep Time: 25 minutes
Cook Time: 50 minutes
Category: Breakfast, Dessert
Cuisine: American