Moist Banana Crumb Cake

Banana crumb cake turns a handful of spotty bananas into a soft, tender crumb crowned with thick, buttery streusel. It’s the kind of cake that feels like a weekend treat but comes together with pantry staples and zero fuss.

The cake stays moist even the next day, and that crumb topping bakes up crisp on top, slightly soft where it meets the cake. If you need a bake that uses up overripe bananas and smells like a coffee shop while it’s in the oven, this is the one.

Why This Banana Crumb Cake Stays Moist for Days

The banana isn’t just flavor here; it’s the main source of moisture. Overripe bananas, the ones with black speckled skins, give the cake a deep sweetness and a dense, velvety crumb that never dries out. A little sour cream in the batter adds richness and keeps it tender, even after a day on the counter.

The crumb topping is simple but the ratio is what makes it work. More butter than flour means it forms big, craggy clumps that stay crisp on top and slightly soft where it meets the cake. That contrast is what keeps me slicing off one more piece.

Ingredients

• 2 cups all-purpose flour, spooned and leveled: using the spoon-and-level method prevents a dense cake.
• 1 tsp baking soda
• 1 tsp baking powder
• 1/2 tsp fine sea salt
• 1 cup granulated sugar
• 1/2 cup unsalted butter, melted and cooled slightly
• 2 large eggs, at room temperature
• 1 tsp vanilla extract
• 1 cup mashed very ripe banana (about 2 large bananas)
• 1/2 cup full-fat sour cream, at room temperature

Crumb Topping

• 3/4 cup packed light brown sugar
• 3/4 cup all-purpose flour
• 1 tsp ground cinnamon
• 1/2 cup unsalted butter, cold and cubed

Variations / Substitutions

• Swap sour cream for full-fat Greek yogurt: the crumb will be slightly tangier and just as tender.
• Add 1/2 cup chopped walnuts or pecans: stir them into the crumb mixture for a nutty crunch.
• Use melted coconut oil in the cake batter: replace the melted butter 1:1 for a dairy-free cake, but keep cold butter in the topping for the right texture.
• Double the recipe for a 9×13-inch pan: use two eggs and double all other ingredients; bake time will be 40 to 50 minutes.

If you have extra bananas, try our Banana Chocolate Chip Muffins for another easy bake.

How to Make Banana Crumb Cake

Step 1: Whisk the Dry Ingredients

Preheat your oven to 350°F (175°C) and grease a 9-inch square baking pan. In a medium bowl, whisk together the 2 cups flour, 1 tsp baking soda, 1 tsp baking powder, and 1/2 tsp salt until evenly combined.

That quick whisk distributes the leaveners and salt so the cake rises evenly and the top stays level. Skipping it can leave you with a domed center or a dense lower half.

Step 2: Combine the Wet Ingredients

In a large bowl, whisk the 1 cup granulated sugar with the 1/2 cup melted butter until smooth, about 1 minute. Add the 2 eggs one at a time, beating after each, then stir in the 1 tsp vanilla, 1 cup mashed banana, and 1/2 cup sour cream until no streaks remain.

The batter will look a little curdled when you add the banana and sour cream; that’s normal and will smooth out as soon as you fold in the flour.

Step 3: Cut Together the Crumb Topping

In a small bowl, mix the 3/4 cup brown sugar, 3/4 cup flour, and 1 tsp cinnamon. Add the 1/2 cup cold cubed butter and cut it in with a pastry blender or your fingertips until the mixture forms large, pea-sized clumps. This will take about 2 minutes by hand.

The clumps should look chunky, not powdery. That’s what bakes into crisp, buttery nubs on top of the cake. If the butter starts to soften, pop the bowl in the fridge for 5 minutes.

Step 4: Assemble and Bake the Cake

Pour the wet ingredients into the dry and fold gently with a spatula just until you no longer see dry flour. Overmixing is the fastest way to a tough cake, so stop as soon as the batter comes together. Scrape the batter into the prepared pan and spread it into the corners.

Pile the crumb topping evenly over the top, pressing some of it lightly into the batter so it adheres. Bake for 45 to 55 minutes, until a toothpick inserted in the center comes out clean or with a few moist crumbs. If the topping browns too quickly, tent the pan loosely with foil during the last 10 minutes.

Step 5: Slice and Serve the Cake

Let the cake cool in the pan for 15 minutes before slicing; that gives the crumb time to set. Slice into squares and serve warm, or let it cool completely for cleaner cuts.

Serve it straight from the pan with a dusting of cinnamon on top. The crumb will be golden and crisp, with a tender, banana-scented crumb underneath.

How to Get the Crumb Topping Just Right

• For the deepest banana flavor, use bananas that are heavily speckled or even black-skinned. They mash to a near-liquid that infuses every bite.
• If your crumb topping starts to brown too much, tent the pan loosely with foil for the last 10 minutes of baking.
• The cake tastes even better the next day, so it’s a great make-ahead bake. The banana flavor intensifies as it sits.
• A serrated knife makes the cleanest slices through the crumb without tearing it.

Bake times by pan:

Storing Leftovers

Refrigerate Cover tightly and store at room temperature for up to 3 days, or refrigerate for up to a week. The crumb will soften over time, but the cake stays moist.

Reheating Warm individual squares in a 300°F oven for 5 minutes to recrisp the topping.

What to Serve With Banana Crumb Cake

A strong cup of black coffee is the classic partner: the bitterness cuts through the sweet crumb. For dessert, drizzle a little warm maple syrup over a warmed slice or add a scoop of vanilla ice cream, the cold cream against the warm cake is hard to beat.

Frequently Asked Questions

Can I freeze this cake?

Yes, wrap the cooled cake tightly in plastic wrap and foil and freeze for up to 3 months. Thaw at room temperature, then warm in the oven to bring back the crisp topping.

Why is my cake dense?

Overmixing the batter once you add the flour, or using bananas that aren’t ripe enough, can weigh the cake down. Fold just until the flour disappears, and use bananas with speckled skins.

My crumb topping sank into the batter. What went wrong?

The batter was too thin, or you pressed the crumb in too firmly. Spread the batter evenly, then sprinkle the crumb on top with light pressure so it stays on the surface.

Can I use oil instead of butter in the topping?

No, the topping needs solid butter to form the clumps that get crisp. You can substitute melted coconut oil in the cake batter if needed, but keep cold butter for the crumb.

Banana Crumb Cake Recipe

Print Recipe Pin Recipe

Prep Time 15 minutes mins

Cook Time 50 minutes mins

Total Time 1 hour hr 5 minutes mins

Servings: 9 servings

Calories: 513

Ingredients Method Notes

Ingredients

  

• 2 cups all-purpose flour, spooned and leveled
• 1 tsp baking soda
• 1 tsp baking powder
• 1/2 tsp fine sea salt
• 1 cup granulated sugar
• 1/2 cup unsalted butter, melted and cooled slightly
• 2 large eggs, at room temperature
• 1 tsp vanilla extract
• 1 cup mashed very ripe banana (about 2 large bananas)
• 1/2 cup full-fat sour cream, at room temperature
• 3/4 cup packed light brown sugar
• 3/4 cup all-purpose flour
• 1 tsp ground cinnamon
• 1/2 cup unsalted butter, cold and cubed

Method

 

1. Preheat oven to 350°F (175°C). Grease a 9-inch square baking pan. Whisk together flour, baking soda, baking powder, and salt.
2. In a large bowl, whisk sugar and melted butter until smooth. Add eggs one at a time, then vanilla, mashed banana, and sour cream until combined.
3. In a small bowl, mix brown sugar, flour, and cinnamon. Cut in cold butter until large clumps form.
4. Fold wet mixture into dry just until no flour streaks remain. Spread into pan and top evenly with crumb. Bake 45–55 minutes, until a toothpick comes out clean.
5. Cool in pan 15 minutes, then slice and serve warm.

Notes

Let the cake cool completely before storing to keep the topping from getting gummy. If you only have an 8-inch pan, the cake will be thicker and need a few extra minutes in the oven.