Rhubarb Cake with Vanilla Butter Sauce

But Wait… What is Rhubarb?!

Though technically a vegetable, rhubarb is a “culinary fruit,” meaning it’s typically prepared as a fruit in the kitchen. Rhubarb is a perennial and has long stalks with a large, dark green leaf on the end. The stalks look kind of like reddish celery, but bring a tart, vibrant flavor, perfect for baking! It’s a popular commodity in the United Kingdom as well as in the Midwestern states of the US (that’s me!) 😉

But please note: rhubarb leaves are very toxic to humans and animals because they contain high levels of oxalic acid. Never eat the leaves! 

Key Ingredients

The full list of ingredients and amounts are in the recipe card below, but I wanted to draw attention to a few of them.

• Butter – I prefer salted butter, but unsalted butter can also be used.  Make sure the butter is at room temperature so it can easily be incorporated into the cake!  You’ll need butter for the cake and the sauce
• Buttermilk – Or you can make your own with milk and vinegar (more details below).
• Diced Rhubarb – Red typically looks prettier in dishes; green tends to have thicker stalks, but you can use whichever you’ve got on hand! Fresh is better, but you can make this with frozen rhubarb.  
• Strawberries – This is totally optional, but delicious. I recommend using 2 cups of rhubarb and 1 cup of strawberries. Cut the strawberries into small pieces (about the same size as your rhubarb pieces) and add them when you add the rhubarb!

How to Make Rhubarb Cake with Vanilla Butter Sauce

Make the Rhubarb Cake

Start by preparing the pan.  You can either coat the pan in cooking spray or line the pan with parchment paper.  Parchment paper makes for super easy removal from the pan!

Next, you’ll cream the butter and sugar.  Then, add the wet ingredients (egg, vanilla, and oil).  

Preparing Rhubarb for Baking

People often ask if rhubarb needs to be peeled before adding it to a recipe.  I’ve never peeled a stalk of rhubarb in my life! It’s only the leaves you have to worry about. So, once you pick the stalk, you’ll want to cut both ends off (the leaves will be tossed, as will the light colored part that was taken from the ground).  Wash the rhubarb in cold water and pat dry.  Cut into 1/2 inch pieces and add to the cake batter!

Can’t find fresh rhubarb? That’s ok…you can use frozen rhubarb, with a couple of things to keep in mind. Make sure the rhubarb is cut into small pieces before freezing. Large chunks can release a lot of moisture as they bake, creating overly wet pockets in the cake.

There’s no need to thaw the rhubarb first. Just add it to the batter while it’s still frozen, and keep in mind that your cake may need a little extra time in the oven.

Now it’s time to add half of the dry ingredients, followed by the rhubarb and finally the remaining dry mixture. Stir in the rhubarb until well-dispersed and spread it into the prepared pan.

Bake the cake for 40-45 minutes or until a toothpick pressed into the center of the cake comes out with just a few moist crumbs.  Remove from the oven and let it cool on a wire rack.

Pro tip:  If you are smart and doubled the recipe, you’ll be SO glad you did! 🙂 Simply bake as instructed, but just a note that it’ll likely take an additional few minutes.

Please note that different cake pans and different ovens can alter the cook time.  I recommend always checking the cake at the earliest time listed and go from there! (You can always bake longer….but you can’t “unbake” if it’s overdone!)

Make the Butter Sauce

Making the sauce is simple! You’ll stir the heavy cream, sugar, and butter together in a saucepan and bring it to a boil. Let it boil for 5 minutes, then remove from the heat and stir in the vanilla. You can enjoy this warm or when it’s cooled to room temperature. It’ll thicken a bit in the fridge, so you might want to warm it up in the microwave if using later on!

How to Serve Rhubarb Cake

This cake is truly delicious on its own.  It’s moist, delicate and has lots of juicy rhubarb throughout!  However, if you want to take it up a notch, make the super simple vanilla rhubarb sauce!!  It pairs beautifully with the cake.  Add the sauce and/or a scoop of vanilla ice cream (or whipped topping!) and enjoy!!!

How to Store Leftover Rhubarb Cake  

Because the rhubarb brings lots of moisture to the cake, I recommend storing it in the fridge if you don’t plan to eat it all in the first day or two.  It’ll keep in the fridge in an airtight container for up to 5 days.