Moist & Spiced Sourdough Banana Cake

This recipe uses sourdough discard and a jelly roll pan for quick baking and an extra-soft texture. It’s soft, spiced just right with cinnamon, and comes together fast: no creaming butter, no waiting forever for a loaf to bake. 

Ingredients and Tools You’ll Need

Just pantry ingredients and couple ripe bananas! And once you try this and my sourdough banana bread, you’ll always have bananas on hand!

For the Cake

• 2 very ripe bananas, mashed
• ½ cup granulated sugar
• ½ cup brown sugar
• ½ cup vegetable oil
• 2 eggs
• 1 teaspoon vanilla extract
• 2 cups all-purpose flour
• 1 teaspoon baking soda
• 1 teaspoon baking powder
• ½ teaspoon salt
• 2 teaspoons ground cinnamon
• ½ cup sourdough starter discard or unfed (active starter is fine too)

For the Frosting

• 4 ounces cream cheese, room temperature
• 6 tablespoons butter, room temperature
• 1 teaspoon vanilla extract
• 2½ cups powdered sugar (if your powdered sugar is lumpy, sifting it will help the frosting stay smooth)

How to Make Sourdough Banana Cake

This is easy. Promise.

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Step 1: Mash the bananas and mix the wet ingredients

Start by mashing two very ripe bananas in a large mixing bowl. The riper they are, the better. Use a large bowl! You’ll be adding the dry ingredients next.

Once they’re mashed, add the granulated sugar, brown sugar, and vegetable oil. Use a hand mixer or whisk to beat them together until fairly smooth. It’s okay if there are still a few banana lumps. Then add the eggs and vanilla and mix again until everything is fully combined.

Step 2: Add the dry ingredients right into the bowl

No need to mix the dry ingredients in a separate bowl—just add them straight into the wet mixture to keep things simple. Sprinkle in the flour, baking soda, baking powder, salt, and cinnamon.

Start your mixer on low so the flour doesn’t puff everywhere, and blend until the batter is just combined. Don’t overmix! Stop when the flour disappears and the texture looks mostly smooth.

Step 3: Stir in the sourdough discard

Now add your sourdough starter discard. It should be unfed but not overly hungry.

Stir it in by hand with a wooden spoon or spatula to avoid overmixing the batter.

Step 4: Spread the batter into your jelly roll pan

Grease a 10×15-inch jelly roll pan with nonstick spray or shortening and flour. Then pour the batter into the pan and smooth the top evenly.

Jelly roll pans are shallow, so they bake faster and give that just-right cake to frosting ratio.

Step 5: Bake until golden and springy

Bake at 350°F for about 17 to 20 minutes. Start checking at 17 minutes. If the top springs back when lightly touched and a toothpick in the center comes out clean, it’s done.

Let the cake cool completely in the pan before frosting.

Step 6: Make the frosting

While the cake cools, beat the cream cheese and butter until smooth. Add the vanilla, then beat in the powdered sugar a little at a time until everything is creamy and spreadable.

Room temperature ingredients are key here! Cold butter or cream cheese will make your frosting lumpy.

Step 7: Frost and serve

Spread the frosting over the cooled cake, smoothing it all the way to the edges. This cake cuts beautifully into neat squares—perfect for serving a crowd.

Storage and Make-Ahead Tips

Cover the cake tightly and store it in the fridge for up to 5 days. Let it sit at room temperature for 15–20 minutes before serving for the best texture. You can also bake the cake a day ahead and frost it just before serving.

Printable Recipe

Sourdough Banana Cake

Moist, flavorful, and finished with the best cream cheese frosting, this sourdough banana cake is a great way to use up starter discard. Bakes in under 20 minutes in a jelly roll pan—no loaf pan, no long wait.

Print Recipe

Prep Time:15 minutes mins

Cook Time:20 minutes mins

Cooling time:1 hour hr

Total Time:35 minutes mins

1x2x3x

Ingredients

For the Cake

• 2 very ripe bananas mashed
• ½ cup granulated sugar
• ½ cup brown sugar
• ½ cup vegetable oil
• 2 eggs
• 1 teaspoon vanilla extract
• 2 cups all-purpose flour
• 1 teaspoon baking soda
• 1 teaspoon baking powder
• ½ teaspoon salt
• 2 teaspoons ground cinnamon
• ½ cup sourdough starter discard/ unfed state

For the Frosting

• 4 ounces cream cheese room temperature
• 6 tablespoons butter room temperature
• 1 teaspoon vanilla extract
• 2½ cups powdered sugar

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Instructions

The cake

• Prep. Preheat oven to 350°F. Grease a 10×15-inch jelly roll pan with baking spray or shortening and dust lightly with flour.
• Beat wet ingredients + sugar. In a large bowl, beat together the mashed bananas, granulated sugar, brown sugar, and oil. Add the eggs and vanilla and mix until smooth.
• Add ingredients. Add the flour, baking soda, baking powder, salt, and cinnamon directly into the bowl. Mix until just combined. Stir in the sourdough discard by hand.
• Bake. Pour the batter into the prepared pan and smooth the top. Bake for 17–20 minutes, or until the top springs back when lightly touched and a toothpick inserted in the center comes out clean. Let cool completely in the pan.

The frosting

• Make frosting. Beat the cream cheese and butter until smooth. Add the vanilla and beat to combine. Add the powdered sugar in two batches, mixing on low, then beat briefly on medium until smooth.
• Assemble. Spread frosting over the cooled cake and cut into squares to serve.

Notes

This cake also works well in a 9-inch square or round pan—bake for 45–50 minutes.
Don’t like cream cheese frosting? A caramel glaze or dusting of powdered sugar would be great too.
Store covered in the fridge for up to 5 days.

Nutrition

Calories: 355kcal | Carbohydrates: 53g | Protein: 3g | Fat: 15g | Saturated Fat: 6g | Polyunsaturated Fat: 5g | Monounsaturated Fat: 4g | Trans Fat: 0.2g | Cholesterol: 41mg | Sodium: 250mg | Potassium: 106mg | Fiber: 1g | Sugar: 36g | Vitamin A: 284IU | Vitamin C: 1mg | Calcium: 40mg | Iron: 1mg

Servings: 15 slices

Calories: 355kcal

Author: Katie Shaw