This rhubarb crumb cake has a soft and moist vanilla cake base topped with a layer of tart fresh rhubarb. A sweet, buttery streusel topping is sprinkled on top, adding a delicious crunch to each bite.
It's Spring, and you know what that means- rhubarb season is here! A rhubarb crumb cake is the perfect way to incorporate it into your Spring bakes.
So what is this weird pink celery looking thing anyways? Rhubarb is actually a vegetable that is often used like a fruit in sweet dishes, like pies, cakes, and jams because of its sour flavor. It has long, thick, pinkish-red stalks and large green leaves. It's a popular ingredient in desserts but can also be used in savory dishes like sauces and marinades.
Rhubarb is a truly seasonal crop, typically available in the Spring and early Summer months. Raw rhubarb is incredibly sour, almost as tart as a lemon. That's why it's usually cooked with lots of sugar to make it palatable.
Rhubarb is the perfect addition to crumb cake. This isn't like your typical New York style crumb cake or coffee cake; the vanilla sponge is much more soft, delicate, and moist with a tight crumb. Rhubarb is layered on top of that and sprinkled with a sweet, buttery crumble. The result is Spring in a bite!
Serve this crumb cake at brunch, a Summer BBQ, or with a scoop of vanilla ice cream for an indulgent dessert. You're going to absolutely love it!
Here are some notes about the ingredients used. For quantities and full instructions, see the recipe card below.
- All purpose flour- Using all purpose flour instead of cake flour makes the crumb cake a bit more moist and hearty.
- Granulated sugar- White sugar sweetens the batter and helps the cake retain moisture. It's also used to sweeten the crumble.
- Brown sugar- This adds moisture and sweetness to the crumble. You can use light or dark brown sugar.
- Unsalted butter- Unsalted butter is in the cake and crumble for flavor, richness, and to control the amount of salt in the batter. For the cake, make sure it's at room temperature so it creams in easily. It should be cool to the touch and easy to indent with your finger. Melted butter is best for the crumble since it lends a crisp texture.
- Baking powder- This leavener helps the cake rise by adding air bubbles. Make sure it isn't expired and don't substitute baking soda since it's much stronger.
- Salt- You need a little salt so the cake isn't too sweet and bland.
- Eggs- Two large eggs add moisture, richness, and bind everything together. Make sure they're room temperature so they mix in nicely.
- Vanilla extract- Vanilla enhances all the ingredients and rounds out the flavor profile.
- Buttermilk- If you've made my cakes and muffins before, you know I love buttermilk. It adds a slight tang while tenderizing the gluten for a super soft cake!
- Rhubarb- The star of our recipe! You'll need 3 stalks of rhubarb chopped into 1 inch pieces.
- Orange zest- This is mixed with the rhubarb to add a little citrusy sweetness to mellow the tartness. Any kind of orange works, from navel to Mandarin.
- All purpose flour: To make a gluten free crumb cake, substitute Bob's Red Mill 1-to-1 Gluten Free Baking Flour .
- Unsalted butter: Don't worry if you only have salted butter! Just omit the extra salt.
- Buttermilk: Substitute plain kefir, plain Greek yogurt, or sour cream at a 1:1 ratio. Additionally, you can make your own buttermilk by mixing ½ cup milk with 1 ½ teaspoons vinegar or lemon juice. Let the mixture curdle 10 minutes and it's ready to use.
- Rhubarb: Not a rhubarb fan? No problem! You can make this cake with a variety of fresh fruit, like strawberries, chopped apples, blueberries, or blackberries.
Helpful Equipment and Tools
- A 9x9" square baking pan is needed to bake the cake in. Use a metal pan, not glass or silicone. Glass doesn't heat evenly and silicone can cause your cake to burn. If your pan isn't non-stick, don't forget to spray it with baking spray before lining with parchment paper.
- To mix the cake batter, you need an electric hand mixer. You can also make it with a stand mixer fitted with the paddle attachment.
Step by Step Instructions
Here's how to make a rhubarb crumble cake! Before you start, wash, dry, and chop your rhubarb stalks. Preheat the oven to 350°F/180°C, line your square pan with parchment paper, and set it aside.
STEP 1: First, make the crumble by whisking melted butter, sugar, brown sugar, and flour together in a small bowl until clumpy. Set in the the fridge until you're ready to use it.
STEP 2: Stir together the all purpose flour, sugar, baking powder, and salt in a large mixing bowl with a whisk.
STEP 3: Add the softened butter to the dry ingredients. Beat on low with a hand mixer for 5 minutes or until the texture is sandy. This is called the reverse creaming method.
STEP 4: With the mixer running on low, add the eggs and vanilla.
STEP 5: Stream in the buttermilk next. Continue to mix on medium speed until the batter is combined with no puddles of liquid.
STEP 6: Pour the batter into your prepared baking pan. Spread it evenly across the pan with an offset spatula or the back of a spoon. Set aside.
STEP 7: Next, toss the chopped rhubarb and orange zest together in a medium mixing bowl.
STEP 8: Evenly sprinkle the rhubarb over the cake batter. Don't press the rhubarb in, just make sure it lays evenly on top of the batter.
STEP 9: Next, take the crumble out of the refrigerator and sprinkle it all over the top of the rhubarb. Bake the cake for 40-50 minutes or until a toothpick inserted in the center comes out clean with a few moist crumbs.
STEP 10: Let the cake cool for 20 minutes, then pull the parchment up, lifting the cake out of the pan onto a wire cooling rack. Let it cool on the rack for 30 minutes or until it reaches room temperature. Dust with powdered sugar, slice, and enjoy!
Expert Baking Tips
- Don't eat the leaves. Your fresh rhubarb might have leaves on it, but make sure to cut them off because they're actually poisonous!!
- Use a kitchen scale. For accuracy and consistent results, measure the flour in grams with a food scale instead of using cup measurements. If you don't have a scale, fluff the flour up first before spooning it into your measuring cup.
- Chill the crumb topping. Let the crumb topping chill in the fridge for at least 10 minutes before sprinkling it on the cake. This prevents it from melting into the cake and helps it hold its shape.
- Don't skimp on the crumble! The crumb topping is buttery and sweet, which contrasts the sourness of the rhubarb. Be generous with it!
Additions and Variations
Here are some extra ingredients you can add to the cake! Note that I haven't tried any of these myself, so let me know how it turns out below.
- Nuts: Chopped almonds, pecans, or walnuts add a delicious crunch to the topping or to the cake batter itself.
- Spices: Adding spices like cinnamon, nutmeg, or ginger to the cake batter or crumble topping can give your rhubarb crumb cake an extra kick of flavor.
- Lemon zest: A little bit of lemon zest adds a bright, fresh flavor to the tangy rhubarb and rich streusel. You can add this or substitute it for the orange zest.
Storage and Freezing
Leftover crumb cake stays fresh for 2-3 days at room temperature. Just wrap it up in plastic or store in an airtight container. Don't put it in the fridge because it can make the cake dry and the crumb topping mushy.
Freeze cut slices in a sealed, freezer-safe container for up to 1 month. When you're ready for a slice, let it thaw on the counter for a few hours or in the fridge overnight.
Frequently Asked Questions
You can find rhubarb at farmer's markets, co-ops, and some larger grocery stores like Whole Foods when it's in season. Rhubarb season starts in late March and lasts through July.
You sure can! You can use an 8x8" pan or 9x13" baking dish. It'll be really thin in a 9x13" pan, so I recommend doubling the recipe if you're planning on using one.
Both cakes are slightly different. Coffee cake typically has 2 layers of streusel, one running through the center and one on top. Crumb cakes only have a crumble layer on top.
More Cake Recipes to Try
Rhubarb Crumb Cake
- 3 stalks rhubarb chopped
- 2 tablespoon orange zest
- Chop your rhubarb and set aside. Preheat the oven to 350°F/180°C and lightly grease a 9x9" square baking pan and line with parchment paper. Set aside.
For the Crumb
- Mix the melted butter, granulated sugar, brown sugar, and flour together in a small bowl with a spoon until crumbles form. Place in the fridge to chill.¼ cup unsalted butter, ¼ cup granulated sugar, ¼ cup brown sugar, ½ cup all purpose flour
For the Cake
- Whisk the flour, sugar, baking powder, and salt together in a large mixing bowl until combined.1 ½ cup all purpose flour, 1 cup granulated sugar, 1 teaspoon baking powder, ¼ teaspoon salt
- Add the softened butter and beat on low with a hand mixer or stand mixer until it looks like wet sand.⅔ cup unsalted butter
- Mix in the eggs and vanilla with the mixer on low.2 large eggs, 2 teaspoon vanilla extract
- Stream in the buttermilk as the mixer runs on low. Turn the speed up to medium and mix until smooth and well combined.½ cup buttermilk
- Pour the cake batter into the prepared pan. Spread it evenly with an offset spatula or butter knife.
- Toss the chopped rhubarb and orange zest together in a medium bowl.3 stalks rhubarb, 2 tablespoon orange zest
- Sprinkle the rhubarb on top of the cake batter, not pressing it in.
- Generously sprinkle the crumble on top.
- Bake for 40-50 minutes until a toothpick inserted in the center comes out clean.
- Let the cake cool in the pan for 20 minutes, then pull on the parchment paper to lift the cake out of the pan. Place it on a wire cooling rack and let it come to room temperature. Dust with powdered sugar, slice, and enjoy!