Name: Sourdough Banana Cake
Prep time: 15 min
Cook time: 20 min
Total time: 35 min
Ingredients: 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); 4 ounces cream cheese (room temperature); 6 tablespoons butter (room temperature); 1 teaspoon vanilla extract; 2½ cups powdered sugar

This sourdough banana cake feels like something that’s been passed down: simple, sturdy, and made from what you already have on hand. It’s the kind of recipe you’d find clipped to a fridge or tucked in a handwritten cookbook, ready whenever the bananas on the counter start to spot. An extra-frugal sourdough discard recipe for those of you who never let anything go to moist.

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Close-up of banana cake topped with frosting, cut into squares in a jelly roll pan.

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!

Overhead view of sourdough banana cake ingredients labeled and arranged on a marble surface.

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)

If you’d like to double or triple this recipe, you can make adjustments in the recipe card at the bottom of this post.

How to Make Sourdough Banana Cake

This is easy. Promise.

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.

Bowl of blended banana, sugar, and oil with beaters resting on the edge.

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.

plit image: dry ingredients added to wet batter, then fully mixed banana cake batter.

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.

Smooth cake batter in a mixing bowl with a wooden spoon resting inside

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.

Split image: batter spread in a pan, then the fully baked cake in the same pan.

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.

Split image: powdered sugar in a bowl, then cream cheese frosting beaten smooth with a mixer.

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.

Banana cake cut into squares and frosted with cream cheese icing in baking pan.

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

Prep Time:15

Cook Time:20

Cooling time:1

Total Time:35