Blackberry Rhubarb Buttermilk Cake

The Story Behind This Blackberry Rhubarb Buttermilk Cake

I first made this blackberry rhubarb buttermilk cake on a rainy spring weekend when I was stuck indoors with an abundance of rhubarb from our garden. I love blackberries and wanted to try them with rhubarb instead of the usual strawberry pairing. I adapted a favorite Gourmet buttermilk cake recipe, and the fruit sank to the bottom during baking, so I served it upside down to show off the pretty berries and rhubarb. That happy accident turned into a go-to summer dessert: no frosting needed, just a crunchy turbinado sugar top.

Why You’ll Love This Easy Blackberry Rhubarb Buttermilk Cake

• The buttermilk makes the crumb incredibly tender while keeping the cake from being too sweet.
• Blackberries burst with sweetness against the tart rhubarb for a perfect balance.
• No frosting needed, just a sprinkle of turbinado sugar on top gives it a crunchy, caramelized crust.

Key Ingredients for the Best Buttermilk Cake

• Buttermilk: Use well-shaken buttermilk for the most tender crumb. It reacts with the baking soda to help the cake rise and stay moist. If you don’t have buttermilk, you can make a quick substitute by adding 1/2 tablespoon of lemon juice to 1/2 cup of milk and letting it sit for 5 minutes.
• Blackberries: Fresh blackberries hold their shape best. If using frozen, don’t thaw them first or they’ll bleed too much color into the batter.
• Rhubarb: Choose firm, crisp stalks. Avoid very thick ones which can be stringy. Cut into small (about 1/2-inch) chunks so they soften during baking.

Kitchen Tools for This Summer Cake

• 9-inch round cake pan, the right size ensures even baking
• Electric mixer (hand or stand) for creaming butter and sugar
• Mixing bowls, whisk, rubber spatula
• Cooling rack for turning out the cake
• Cooking spray or butter for greasing the pan

Tips for a Perfect Blackberry Rhubarb Buttermilk Cake

When mixing the batter, alternate the dry ingredients and buttermilk in three additions, starting and ending with flour. This prevents overmixing, which can make the cake tough. After spooning the batter into the pan, scatter the blackberries and rhubarb evenly over the top rather than folding them in, they’ll sink slightly during baking, creating a beautiful fruit layer on the bottom (which becomes the top when you invert the cake). Don’t skip the turbinado sugar: it melts into a crackly, sweet crust that balances the tart fruit. Let the cake cool in the pan for about 10 minutes before turning out onto a rack to cool completely; this keeps it from sticking.

Blackberry Rhubarb Buttermilk Cake Variations

Try swapping the blackberries for raspberries or blueberries, both work well. For a classic strawberry-rhubarb version, replace the blackberries with an equal amount of strawberries. You can also substitute the lemon zest with orange zest for a different citrus note. If you want a gluten-free option, use a good quality 1-to-1 gluten-free flour blend; the texture may be slightly different but still delicious.

How to Serve This No-Frosting Cake

I like to serve this cake upside down so the fruit is front and center. A dollop of lightly sweetened whipped cream or a scoop of vanilla ice cream makes it even more indulgent, but it’s lovely on its own with a cup of coffee or iced tea. You can also dust the top with a little powdered sugar for a prettier presentation.

How to Store Leftover Buttermilk Cake

Store the cake in an airtight container at room temperature for up to 2 days. For longer storage, refrigerate it for up to 4 days. The fruit may release a little moisture over time, so the cake is best within the first day or two. Bring refrigerated slices to room temperature before serving for the best texture.

Can You Freeze This Blackberry Rhubarb Cake?

Yes, you can freeze the cake. Wrap it tightly in plastic wrap and then foil after it has cooled completely. Freeze for up to 3 months. Thaw overnight in the refrigerator or at room temperature. The texture may soften slightly due to the fruit’s moisture, but it will still taste great.

How to Reheat This Cake

If you prefer to eat the cake warm, reheat individual slices in a 300°F oven for 5 to 10 minutes. Avoid the microwave, which can make the cake soggy. The cake is best at room temperature, but a gentle warm-up can bring back that just-baked feel.

Blackberry Rhubarb Buttermilk Cake FAQs