Blueberry Rhubarb Streusel Cake

As I write this post, there is a Blueberry Rhubarb Streusel Cake in the oven. I should have eaten dinner before I started baking, because the aroma is driving me mad. 

It will be part of our Father’s Day lunch with friends, after vichyssoise, chicken salad, vegetables, and good bread. If I get the chance, I might come up with an appetizer or two as well. But the star of the show will be this cake. 

The idea for this cake started with rhubarb. This rather bizarre-looking fruit (at least to me) is only in season for a few months around the mid-Atlantic US, where I live. The Kitchn (one of my favorite food information sites) says rhubarb is in season from mid-spring throughout the summer, with a prime season of three months from April through June. Maybe that’s true in theory. However, in my neighborhood, rhubarb only seems to be in stores in May and June. So when I saw it last week, I pounced. 

At first, I considered using the rhubarb for a crisp or a crumble. But I had Father’s Day in mind, and thought those desserts weren’t quite festive enough. Then I got fixated on streusel. Soon, I was checking out coffee cake recipes, pondering how to include rhubarb in the cake, and researching streusel.

In the end, this cake is not from any one recipe. But I would be remiss if I didn’t credit the inspiration that I got from this plum streusel coffeecake with a little help from these rhubarb strawberry streusel bars.

It may seem as though the cake has quite a few ingredients. Still, with the exception of rhubarb and maybe the blueberries, they are all pantry staples if you like to bake. The streusel is really only five ingredients. I put the confectioner’s sugar here because it goes on top of the streusel, but listed it after the cake because you don’t need it until the cake has cooled and you’re ready to serve it. 

The cake itself is a simple coffee cake.

If you’re into streusel and want to know what differentiates it from crumb topping, you should read this post. Although I did find the streusel vs. crumb topping discussion helpful, I have to note that this streusel uses melted, rather than cold, butter. The post is just wrong when it says that melted butter causes streusel to flatten out. My secret is letting the streusel sit for a few minutes, then crumbling it with your fingers. It works. Don’t trust me – try it. 

My blueberry rhubarb streusel recipe is a three-layer affair, almost equally divided between coffee cake, fruit and streusel. 

As you can see, there is just enough cake in this Blueberry Rhubarb Streusel Cake to give the fruit and streusel a base to sit on. I consider streusel to be one of the great joys of eating coffee cake, so adding as much of it as I could reasonably put on top of this cake made me incredibly happy. 

And speaking of happy, my beloved looked pretty happy when he wandered into the kitchen and discovered this cake baking for our Father’s Day lunch. Which made me even happier. 

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Blueberry Rhubarb Streusel Cake

A moist cake layered with fruit and streusel. It's perfect for celebrations or weekend munching. 

Course Dessert

Cuisine American

Prep Time 30 minutes

Cook Time 1 hour 10 minutes

Total Time 1 hour 40 minutes

Servings 8 servings

Author Laura

Ingredients

Streusel

• 1 3/4 cups flour
• 3/4 cup light brown sugar, firmly packed
• 1 teaspoon cinnamon
• 1/4 teaspoon ground nutmeg
• 12 tablespoons unsalted butter, melted (1 1/2 sticks or 3/4 cup)

Cake (Batter and Fruit)

• 8 ounces rhubarb, cut into pieces about 1/3-inch thick About 2 cups. Be careful to only use the red stalk of the rhubarb - the leaves are poisonous!!
• 8 ounces blueberries About 2 cups
• 1 tablespoon fresh lemon juice
• 3/4 cup granulated (white) sugar, divided
• 1 1/4 cups flour
• 1 teaspoon baking powder
• 1/2 teaspoon fine sea salt
• 1/3 cup canola (or similar) oil
• 4 tablespoons unsalted butter, at room temperature
• 2 large eggs
• 1 teaspoon vanilla
• 1/3 cup sour cream
• 2-3 tablespoons confectioners sugar For sifting over cake just before serving.)

Instructions

1. Preheat oven to 350°F. and butter and flour a 9-inch round or square baking pan at least 2 inches deep.

Streusel

1. Mix the flour, sugar, cinnamon and nutmeg. Pour the melted butter over the mixture and toss with a rubber spatula just until it forms large crumbs. Set aside. 
   

Cake

1. Mix the rhubarb pieces, blueberries, lemon juice and ¼ cup sugar in a bowl and set aside.
   
2. Whisk together the flour, baking powder, and salt and set aside. 

3. Put the butter, canola oil, and sugar in a medium bowl. Beat them with an electric mixer or whisk until the mixture becomes light and fluffy (about 2 minutes with an electric mixer.) Add the sour cream and mix until combined. Then add the eggs, one at a time, beating well after each addition, and then vanilla. Sift in the dry ingredients and mix them in until just combined.

   
4. Spread the cake batter in the pan, smoothing the top so that it is even and pushing the batter out to the edges of the pan. (The batter is spoonable, not runny.) Using a slotted spoon to drain any juices, spread the fruit over the batter. 
   
5. Spread the streusel over the fruit, using your hands to sprinkle it and break up the pieces into irregularly shaped pieces of varying sizes. 
   
6. Bake the cake in middle of oven for 1 hour 10 minutes, or until a tester comes out clean. Cool the cake completely in the pan on a wire rack. Once cooled, run a knife around the edges, put a cutting board or large flat plate on the top and flip the cake out of the pan. Then turn it right side up with another plate or a platter. 
   
7. Just before serving (at room temperature), sift confectioners sugar on top.