sourdough Discard Vegan banana Cake

Remember those squares of super moist, delightfully sweet banana cake we used to get at gas stations on road trips? That’s the cake I wanted to recreate, only vegan. The gas station version wasn’t sourdough, but this one captures what I remember about it best. It’s moist, sweet, and full of banana flavor.

If you’ve got three or four spotty bananas on the counter and a jar of sourdough discard in the fridge, you’re well on your way to banana cake. There are plenty of sourdough discard recipes out there, but the list gets a lot shorter when you’re looking for vegan ones. This cake uses half a cup of discard and gets a generous layer of tangy vegan cream cheese frosting.

About halfway through baking, the kitchen starts to smell like banana bread. That’s the ripe bananas and cinnamon, with a little nutmeg and ginger in the mix. Once the cake cools, spread the vegan cream cheese frosting right over the top. That little bit of tang is so good with the sweet banana cake.

That little square of gas station banana cake is exactly the kind of thing that inspires me in the kitchen. I’ve made it my mission to recreate the foods we’ve always loved and make them vegan. That’s how recipes like great aunt's chocolate Texas sheet cake, a childhood favorite baked mac and cheese, and a reader's favorite tater tot breakfast casserole found their way to Veggie Fun Kitchen. And now there’s a road-trip banana cake to go with them.

Why you’ll love this vegan banana cake

• It puts half a cup of discard to work. Use it straight from the fridge. Baking powder gives the cake its lift, so there’s no rise time.
• You can mix the batter by hand. A fork takes care of the bananas, and a spatula brings the batter together. Save the mixer for the frosting.
• It’s a frost-and-serve kind of cake. Bake it in a 9-inch square pan, spread the frosting right over the top, and cut it into nine generous squares.

And If you still have discard in the jar, try my vegan sourdough discard strawberry swirl coffee cake next. It has ribbons of strawberry and a buttery vanilla crumb topping.

Ingredients you’ll need

For the banana cake

• Very ripe bananas. Look for peels with plenty of brown spots and fruit that gives easily under a fork. Three or four bananas will usually do it, depending on their size. Measure 1¼ cups after mashing so you get the right amount of banana in the batter.
• Packed brown sugar. Press it into the measuring cup, then mash it into the bananas. The little bit of molasses flavor goes especially well with the cinnamon.
• Sourdough discard, plant milk, avocado oil, and vanilla. Add these once you’ve mashed the brown sugar into the bananas. If the discard falls from the measuring cup in a thick ribbon, stir until it’s blended into the wet ingredients.
• All-purpose flour, baking powder, and salt. Spoon the flour into the measuring cup and level it off. Scooping right from the bag can pack extra flour into the cup.
• Cinnamon, nutmeg, and ginger. You’ll use a teaspoon of cinnamon and just a quarter teaspoon each of nutmeg and ginger. There’s enough spice to warm up the cake while still letting the banana come through.

For the vegan cream cheese frosting

You’ll need vegan stick butter, vegan cream cheese, vanilla, a pinch of salt, and powdered sugar. Set the butter and cream cheese out to soften before you start the cake. Have 2¼ cups of powdered sugar on hand, then start with 2 cups and see how the frosting feels under the spoon. In fact, the recipe I use to frost this banana cake is just a scaled down version of my favorite refrigerator vegan cream cheese recipe.

How to make sourdough discard banana cake

Prep the pan and mash the bananas

Preheat the oven to 350°F and grease a 9-inch square baking pan, getting into the corners. You can use vegan butter or shortening to grease your pan. I like the flavor of butter.

I mash the bananas first and then measure the mashed bananas to get an accurate measurement. It’s important with this recipe that you get the liquids just right because it is already extremely moist.

After you measure out 1¼ cups of mashed bananas, and add the brown sugar. Work the sugar into the bananas with a fork until the mixture looks glossy and the big clumps of sugar have broken up. Stir in the discard, plant milk, avocado oil, and vanilla.

Whisk the dry ingredients, then grab a spatula

In a separate bowl, whisk together the flour, baking powder, salt, cinnamon, nutmeg, and ginger. Give everything a good whisk so the baking powder and spices are evenly distributed before they go into the banana mixture.

Add the dry ingredients to the wet and stir gently. Sweep your spatula along the bottom of the bowl, where pockets of dry flour like to hide. Once the last streak of flour disappears, put down the spatula. A few little pieces of banana in the batter are fine.

Spread the batter evenly into the prepared pan. A 9×9 pan is really the best size for this sourdough discard banana cake. It’s best to use the right-size pan if you can. I very often find an 8×8 pan is the best size (like for the Dolly Parton Cuppa Cuppa Cuppa Cake). In this case though, an 8×8 pan will be too small and the cake will not bake as well unless you use a 9×9 cake pan.

Start checking the middle at 38 minutes

Bake for 38–45 minutes. At 38 minutes, lightly touch the center of the cake. If it springs back, check it with a toothpick. A clean toothpick or a few damp crumbs clinging to it are both good signs. If you see a streak of wet batter, give the cake a few more minutes and check again.

Let the cake cool completely in the pan. Plan on about an hour, then check the middle. If you can still feel warmth there, give it a little longer so the frosting spreads evenly without totally melting.

How to make soft vegan cream cheese frosting

While the cake bakes, beat the softened vegan stick butter, vegan cream cheese, vanilla, and salt until smooth. Scrape down the bowl and look for little flecks of butter. If you see any, keep beating until they disappear. This is the time to get the mixture creamy, since you’ll do very little mixing once the sugar goes in.

Add the powdered sugar one cup at a time, beating just until combined after each addition, up to a minute each time. After the second cup, drag the back of a spoon through the frosting. If it leaves a soft ridge and moves easily under the spoon, it’s ready. If you’d like it thicker, gently fold in more powdered sugar a tablespoon at a time, up to four more tablespoons.

This frosting is meant to be soft and spreadable. If it seems a little loose, give it some time in the refrigerator before deciding whether it needs more sugar. Once the cake is completely cool, spoon the frosting into the center and sweep it out to the edges. Cut the cake into nine squares.

A few questions before you bake

Do I need to feed my sourdough starter first?

Use unfed discard straight from the refrigerator. If you’re feeding your starter that day, measure out half a cup from the portion you remove before feeding.

Can I skip the frosting?

You can… but why? The cream cheese frosting is soooo good! But yes, you can leave it plain for a banana snack cake to go with a cup of coffee, or dust the cooled cake with a little powdered sugar. For the full banana cake experience, I’d go with the cream cheese frosting. That bit of tang is what makes me want another bite.

Can I make the frosting ahead of time?

Yes, if you make the frosting ahead of time then store it in the refrigerator tightly covered. Pull the premade frosting out of the refrigerator while the cake is cooling to make it easier to spread. Straight out of the fridge might tear into the baked banana cake.

How to store it

Keep the frosted cake covered in the refrigerator. You can serve it chilled or let individual slices sit briefly at room temperature to take the chill off before serving.

It’s funny how a little square of banana cake can take you right back to a road trip. I’m glad I finally have a vegan version I can make at home. If you bake it, leave a rating and tell me what you think. And if there’s a road-trip treat you’d love to see made vegan, tell me that too. I’m always up for a new one to try!

Thanks, ❤️
Cindy