8×8 Banana Cake Recipe: Moist Layers with Walnut Streusel Topping

This 8×8 banana cake recipe delivers layers of moist, tender cake topped with a crunchy walnut streusel that keeps every bite interesting. 💛 The secret lies in ripe bananas and a touch of sour cream that keeps the texture perfect while the streusel adds texture contrast.

I’ve perfected this recipe over years of baking, ensuring it stays moist even after slicing.

The recipe uses simple ingredients you likely already have—flour, sugar, eggs, and of course, bananas—but the technique makes all the difference. A 350°F oven ensures even baking, while the walnut streusel adds a satisfying crunch that balances the cake’s softness.

It’s a vegetarian-friendly treat that’s perfect for brunch, dessert, or even a quick snack.

What you’ll end up with is a single 8×8-inch cake with perfectly moist layers and a streusel topping that stays crisp. The aroma alone will have everyone heading to the kitchen, and the first bite delivers that classic banana cake flavor with an added nutty crunch.

This recipe is foolproof and always a crowd-pleaser.

Whether you’re baking for a family gathering or just craving a slice, this banana cake is the answer. The 15-minute prep makes it easy to whip up, and the result is a dessert that tastes homemade but requires no special skills. Let’s get baking!

Ingredients for 8 x 8 banana cake

Simple ingredients that create a perfect 8×8 banana cake with walnut streusel topping.

The bananas are everything here—ripe, with brown spots and that sweet, mushy texture. Grab them from the grocery store’s produce section, or check the back of the bin where they tend to ripen faster. Kroger or Whole Foods usually have the sweetest ones. For the walnuts, Trader Joe’s sells pre-chopped, toasted ones in bulk—no need to toast yourself. The oats? Old-fashioned, not quick, so they blend better into the streusel. If you can’t find them, blend regular oats in a food processor for 10 seconds.

No sour cream? Plain Greek yogurt works in a pinch—just use the same amount. Running low on walnuts? Pecans or almonds add a different but delicious crunch. The baking powder and soda are non-negotiable—Diamond Crystal is my go-to brand, but any good brand works. For the streusel, if you’re feeling fancy, toast the nuts and oats in a dry pan for 3-4 minutes before mixing—they’ll be even crunchier. But honestly, skipping this step won’t ruin it.

This cake keeps beautifully. Wrap tightly in plastic wrap and store at room temperature for 3-4 days, or refrigerate for 1 week. The streusel stays crisp for days, but if it softens, just pop it back in a 300°F oven for 5-7 minutes to refresh. Freezes for 3 months too—just thaw at room temperature before slicing. I always make a double batch because it disappears fast.

Step-by-step instructions for 8×8 banana cake recipe

Here’s the method for a perfectly moist banana cake with a crunchy walnut streusel topping.

Preheat your oven to 350°F and grease an 8×8-inch baking pan with vegetable oil or line it with parchment paper. In a large mixing bowl, mash the 3 medium ripe bananas until completely smooth – you should have about 1 cup of mashed banana. Set aside.

In a separate bowl, whisk together the 2 cups all-purpose flour, 1 tsp baking soda, 1 tsp baking powder, and 0.5 tsp salt. Sift the dry ingredients directly into the mashed bananas to prevent lumps. Add the 1.5 cups granulated sugar, 1 cup vegetable oil, 2 whole large eggs, 0.5 cup sour cream, and 1 tsp vanilla extract to the banana mixture.

While the cake batter rests for 5 minutes, prepare the streusel topping in a medium bowl. Pulse the 1 cup walnuts and 0.5 cup old-fashioned oats in a food processor until finely chopped but not powdery. Transfer to a mixing bowl and combine with 0.25 cup light brown sugar and 1 tsp cinnamon. Mix until evenly distributed – you want a crumbly texture that will hold together when sprinkled.

Here’s the thing – don’t overmix the streusel or it will turn into a paste. You’re looking for a texture that resembles coarse sand when you press it between your fingers. This ensures the perfect balance of crunch and sweetness on top of your cake.

Pour the cake batter into the prepared 8×8-inch pan and spread it evenly. Sprinkle the streusel topping evenly over the batter, pressing down gently with a spatula to help it adhere. The topping should completely cover the batter with no bare spots showing.

Bake for 35-40 minutes or until a toothpick inserted into the center comes out clean. I know it’s tempting to check early, but resist the urge – the cake needs that full baking time to develop proper structure and moisture. The edges should be golden brown while the center remains slightly springy to the touch.

Remove the cake from the oven and let it cool in the pan for 10 minutes. This resting period prevents the cake from cracking as it cools completely. Transfer to a wire rack and cool completely before slicing. Here’s where patience pays off – the cake will firm up as it cools, making it easier to serve perfect slices.

Once completely cool, dust the top with 2 tbsp powdered sugar using a fine-mesh sieve. This final step adds a delicate sweetness that complements the rich banana flavor. Store any leftovers covered at room temperature for up to 3 days, or refrigerate for up to 5 days.

Troubleshooting great 8 x 8 banana cake

Cake Too Dense

If your banana cake turns out dense instead of moist, overmixing is usually the culprit. Once you’ve sifted the dry ingredients into the wet, mix just until combined—about 15-20 strokes with a spatula. Overmixing develops gluten, making the cake tough.

Also, ensure your bananas are very ripe (black spots, mushy texture) and measure your flour correctly—spoon and level it into the cup rather than scooping directly from the bag. 💡

Streusel Too Soft

The streusel should be crumbly but not sticky. If it turns out soft after baking, your oven might be too hot, or the streusel mixture was overmixed. For best results, chill the streusel for 10 minutes before sprinkling it on the cake batter.

If it still doesn’t crisp up, try baking the cake at 325°F instead of 350°F—the lower heat helps the streusel stay crisp while the cake bakes through.

Cake Cracking

Cracks usually appear when the cake cools too quickly. After removing the cake from the oven, let it cool in the pan for the full 10 minutes before transferring to a wire rack.

Avoid placing it on a cold surface—opt for a warm rack or even the countertop for a few minutes longer. If cracks are already forming, try brushing the top with a thin layer of simple syrup (equal parts sugar and water) before baking to add moisture and flexibility.

Uneven Baking

For an 8×8-inch cake, uneven baking often means the center isn’t fully cooked while the edges are overdone. Rotate the pan halfway through baking (after 20 minutes) to ensure even heat distribution.

If your oven runs hot, reduce the temperature to 325°F and add 5-10 minutes to the baking time. A good test is to check the center after 35 minutes—if it’s still slightly springy, it needs more time.

Streusel Not Sticking

If the streusel falls off during baking, it wasn’t pressed down firmly enough. After sprinkling the streusel, use the back of a spoon or a spatula to gently press it into the batter, creating slight grooves for better adhesion.

For extra grip, lightly brush the batter with a tiny bit of melted butter or oil before adding the streusel. This helps the streusel cling to the cake instead of sliding off. 🥜

Dry Cake Texture

A dry cake often results from overbaking or using too much flour. Stick to the 35-40 minutes baking time and pull it out when a toothpick comes out with a few moist crumbs (not wet batter).

If you suspect the flour was overmeasured, try reducing it by 2 tablespoons next time. For added moisture, replace ¼ cup of the vegetable oil with unsweetened applesauce or Greek yogurt in future batches.

Frequently asked questions about 8×8 banana cake