Sour Cream Rhubarb Coffee Cake
Why You’ll Love This Recipe
I remember the first time I tried to make a rhubarb coffee cake. The rhubarb sank right to the bottom and turned into a mushy, sour puddle. It was a total disaster. That is when I started working on this version. The sour cream in the batter is the secret hero here. It keeps the cake incredibly moist and tender while also helping to support the heavy rhubarb pieces so they stay suspended throughout the crumb.
This Sour Cream Rhubarb Coffee Cake solves the classic problem of soggy, sunken fruit. The thick, tangy batter acts like a cozy blanket for every single piece of rhubarb. I tested this cake at least five times to get the texture just right. You get a crunchy, buttery streusel on top, a soft and velvety cake in the middle, and bright, tart pops of rhubarb in every bite. It is the perfect balance of sweet and tangy. If you love the texture of a classic sour cream cake, you will adore this fruity twist. For more on the science of baking with sour cream, you can read about sour cream and how its fat content affects baked goods.
Ingredients
- 2 cups all-purpose flour
- 1 teaspoon baking powder
- 1 teaspoon baking soda
- 1/2 teaspoon salt
- 1/2 cup unsalted butter, softened
- 1 cup granulated sugar
- 2 large eggs
- 1 teaspoon vanilla extract
- 1 cup sour cream
- 2 cups fresh or frozen rhubarb, chopped into 1/2-inch pieces
For the streusel topping:
- 1/2 cup all-purpose flour
- 1/2 cup packed brown sugar
- 1 teaspoon ground cinnamon
- 1/4 cup cold unsalted butter, cut into small cubes
Step-by-Step Directions
- First, get your oven preheating to 350 degrees F. Grease a 9-inch round or square baking pan really well. I like to use a springform pan because it makes the cake look so pretty when you release the sides.
- In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set this bowl aside for now. This step is important because it evenly distributes the leavening agents so you do not get a bitter pocket of baking soda in your cake.
- In a large mixing bowl, beat the softened butter and granulated sugar together. I use a hand mixer on medium speed. Beat for about 3 minutes until the mixture looks light and fluffy. You want to see it get noticeably paler in color. That means you have incorporated enough air for a tender crumb.
- Crack in the eggs one at a time, beating well after each addition. Stir in the vanilla extract. The batter will look a little curdled at this point, and that is totally normal.
- Now, with the mixer on low speed, add about one third of the flour mixture. Then add half of the sour cream. Keep alternating, ending with the flour mixture. Mix only until you cannot see any more dry streaks. Overmixing will make the cake tough.
- Here is the most important part. Gently fold the chopped rhubarb into the batter using a rubber spatula. Do not stir vigorously. You want to coat the rhubarb pieces in the thick batter so they do not sink. The batter will be very thick and almost like a dough.
- Scrape the batter into your prepared pan and spread it out evenly. It will be thick, so take your time.
- For the streusel, combine the flour, brown sugar, and cinnamon in a small bowl. Cut in the cold butter cubes using a pastry blender or your fingertips. You want the mixture to look like coarse, crumbly sand. Sprinkle this all over the top of the cake batter.
- Bake for 45 to 50 minutes. Your kitchen will start smelling like cinnamon and warm butter. The cake is done when a toothpick inserted into the center comes out clean or with just a few moist crumbs. If the top is browning too quickly, tent it loosely with foil during the last 10 minutes.
- Let the cake cool in the pan on a wire rack for at least 20 minutes before slicing. This resting time is critical for the structure to set.
Pro Tips for Success
Do not skip the step of coating your rhubarb in the thick batter. If you dump wet rhubarb into a thin batter, it will sink to the bottom and create a wet, soggy layer. The sour cream makes the batter thick enough to hold the fruit in place.
Your butter for the streusel must be very cold. If it is warm, the streusel will melt into the cake instead of staying in crunchy, crumbly bits on top. I sometimes pop my butter cubes in the freezer for five minutes before cutting them into the flour.
Let the cake cool completely before slicing if you want clean pieces. Warm cake is delicious but very fragile. The crumb needs time to set. For more on the role of butter temperature in baking, check out this butter article.
Servings and Timing
This recipe makes one 9-inch cake, which serves about 8 to 10 people. The total prep time is about 20 minutes, and the baking time is 45 to 50 minutes. So you can have a warm, delicious coffee cake on the table in just over an hour.
Variations and Substitutions
If you do not have fresh rhubarb, frozen rhubarb works perfectly. Do not thaw it first. Just toss the frozen pieces directly into the batter. Thawing will release too much water and make the cake soggy. You can also swap half of the rhubarb for chopped strawberries or raspberries for a different flavor profile. For a gluten free version, use a good quality 1 to 1 gluten free flour blend. The texture will be slightly more delicate, but it still tastes amazing. If you want a less sweet cake, you can reduce the sugar in the batter to 3/4 cup. The sour cream rhubarb coffee cake is very forgiving with small adjustments.
What to Serve With This
This coffee cake is wonderful on its own with a hot cup of coffee. But if you want to make a full brunch spread, I love serving it alongside my Rhubarb Custard Bars for a double rhubarb treat. The creamy custard bars are a perfect contrast to the crumbly coffee cake. A simple side of fresh fruit or a dollop of lightly sweetened whipped cream also pairs beautifully.
Storage and Reheating
Store any leftover coffee cake in an airtight container at room temperature for up to two days. If your kitchen is very warm, you can store it in the fridge, but the cake will dry out a little faster. To reheat, pop a slice in the microwave for about 15 seconds. That brings back the soft, tender texture. You can also warm it in a 300 degree F oven for about 5 minutes. I do not recommend freezing this cake because the rhubarb can become watery when thawed.
FAQs
Can I use Greek yogurt instead of sour cream?
You can, but the cake will be slightly less tender. Sour cream has a higher fat content, which is what makes the crumb so soft and velvety. Greek yogurt will work in a pinch, but the texture will be a little more dense.
My rhubarb always sinks to the bottom. What am I doing wrong?
You are probably using a batter that is too thin. The sour cream in this recipe creates a very thick batter that holds the rhubarb in place. Also, make sure you are folding the rhubarb in gently and not stirring it too much.
Can I make this Sour Cream Rhubarb Coffee Cake in a loaf pan?
Yes, you can. Use a 9×5 inch loaf pan and increase the baking time to about 55 to 60 minutes. Check for doneness with a toothpick. The cake will be a little taller and take longer to bake through.
What if I accidentally use salted butter?
Just reduce or omit the added salt in the batter. The streusel will be a little saltier, but it still tastes great. I have done this before when I was out of unsalted butter and it worked fine.
Can I add nuts to the streusel?
Absolutely. Chopped pecans or walnuts are wonderful in the streusel topping. Add about 1/2 cup of chopped nuts to the streusel mixture. Toast them first for extra flavor.
Conclusion
This Sour Cream Rhubarb Coffee Cake has become a spring tradition in my house. It is the cake I make when the first rhubarb stalks appear at the farmers market. The combination of tangy rhubarb, tender cake, and crunchy streusel is just perfect. I hope you give this recipe a try and enjoy it as much as my family does. Let me know in the comments how it turns out for you.
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