This old-fashioned rhubarb cake can be made with either fresh or frozen rhubarb. A beautiful, moist coffee-cake-style cake, with a brown sugar topping.
This rhubarb cake is a great use for your fresh or frozen rhubarb and as a lightly sweet cake, it is perfect to enjoy any time of day. It bakes up with a brown sugar, cinnamon and nut topping, that provides a nice crispy foil for this lovely moist, coffee-cake-style cake.
This cake is sometimes called “Lunar Rhubarb Cake”, as this cake bakes up with large craters and crevices that resemble a moonscape.
I have halved what is normally a 9×13-inch cake and made it in an 8×8-inch pan here. It can be easily doubled, if you want or need more cake.
Ingredients and Substitutions
Rhubarb – you can use fresh rhubarb or frozen rhubarb in this cake. For frozen rhubarb, use from frozen. No need to thaw. Allow a bit of extra baking time if using frozen rhubarb.
Nuts – you can use chopped walnuts or pecans, or if you don’t want nuts, simply omit them.
Step by Step Photos
- Step 1: Mix up your topping ingredients, dry ingredients and prep your rhubarb.
- Step 2/3: Beat together the butter, sugars, egg and vanilla.
- Step 3/4: Add the flour mixture and the buttermilk (or milk) and mix until well combined.
- Step 5: Fold in the rhubarb (tossed in 1 Tbsp of the flour mixture)
- Step 6: Spoon into prepared 8×8-inch baking pan.
- Step 7: Sprinkle topping mixture evenly overtop of batter.
- Step 8: Bake and enjoy!
Can I double this recipe to make a large cake? Yes! Simply double the recipe and bake in a 9×13-inch baking pan. Increase the baking time by 5-10 minutes. Keep in mind that this cake has a fairly short shelf life (a couple of days), so be sure you can eat the larger cake up in that time to enjoy it at it’s best.
Can I use frozen rhubarb? Yes! You can make this cake with either fresh or frozen rhubarb. No need to thaw the frozen rhubarb.
What is soured milk? “Soured milk” is a bit of an old-fashioned term for what we now refer to as homemade buttermilk, where regular milk is soured by adding either white vinegar or lemon juice and allowing to stand for 10-15 minutes before using.
Can I omit the nuts? Absolutely.
How do I add 1/2 an egg? Simply break an egg into a small cup. Beat with a fork and then divide the mixture in half (just eyeball it). Use one half in the cake, save the other half in the fridge and use for something else (add another egg or two to it for a small batch of scrambled eggs, for example).
Can I skip the egg? Yes! As I have used a halved recipe here, the egg measurement has come out to 1/2 an egg. If you have eggs, you can use 1/2 or put the whole thing in if you don’t think you will use the extra elsewhere. Likewise, you can just skip the 1/2 egg completely.
Can I reduce the sugar? Probably a bit, but bear in mind that rhubarb is very tart. The amount of sugar in the cake, as written, produces a pleasantly, but not overly sweet cake. Reducing the added sugar too much might produce a quite tart cake.
Can I use all white sugar or all brown sugar? Yes! Simply keep to the total amount of sugar (3/4 cup) and use either all white or all brown sugar in that amount.
Storage and Freezing
This cake is best on the day it is baked, especially to enjoy the lovely crisp topping. As it sits longer, the cake and the topping will start to pick up the moisture from the rhubarb and become more and more moist.
This cake can be frozen, though once thawed, would have to be eaten up fairly quickly to avoid an overly moist cake.
Get the Recipe: Old-Fashioned Rhubarb Cake
- 1/2 cup (100 g) white sugar
- 1/4 cup (45 g) brown sugar, see Note 1 below
- 1/4 cup (57 g) butter, at room temperature, salted or unsalted (if salted omit added salt below)
- 1/2 large egg, see Note 2
- 1/2 teaspoon vanilla
- 1 cup (125 g) all purpose flour
- 1/2 cup (113 ml) buttermilk, milk or soured milk, see Note 3 below
- 1/2 teaspoon baking soda
- 1/2 teaspoon baking powder
- 1/2 teaspoon cinnamon
- Generous pinch of salt, omit if using salted butter
- 1 - 1 1/2 cups rhubarb, fresh or frozen, cut into 1/2-inch dice
- 1/2 teaspoon cinnamon
- 1/4 cup (45 g) brown sugar
- 1/4 cup (55 ml) walnuts or pecans, chopped (can omit)
- Preheat oven to 350F. (regular bake/not fan assisted)
- Prepare the topping mixture by stirring together the topping ingredients. Set aside.
- In a medium bowl, whisk together the flour, baking soda, baking powder, cinnamon and salt, if using. Set aside.
- In a bowl with an electric mixer or the bowl of a stand mixer fitted with a paddle attachment, beat together the white and brown sugar, butter, egg and vanilla. *If using frozen rhubarb, toss the rhubarb in 1 Tbsp of the flour mixture, adding the remainder of the flour mixture to the batter.
- Add the flour mixture to the bowl, along with the buttermilk (or milk) and mix until completely blended.
- Fold in rhubarb, then spoon mixture into a greased 8x8-inch baking pan. Sprinkle topping mixture evenly over-top of the batter.
- Bake in preheated oven for about 30-40 minutes (for 8x8 cake), or until cake is golden, pulls away from the sides of the pan and tests clean when tested with a cake tester (be sure you are testing a batter area and not poking moist rhubarb). Frozen rhubarb/light pans will take longest to bake. Fresh rhubarb/dark pans the shortest. 9x13 cakes will take about 45 minutes.
- Allow to cool 10-15 minutes before slicing, to enjoy warm or allow to cool completely, then tightly cover and store at room temperature.
- Cake is best enjoyed on the day it's baked. As it sits longer, the cake starts to pick up moisture from the rhubarb. Cake can be frozen, though it should be enjoyed quickly, once thawed, to avoid an overly moist cake.
2. To get 1/2 an egg, break an egg into a small cup and beat with a fork. Add 1/2 of that to the batter (just eyeball it) and refrigerate the remainder for another use. As it's only 1/2 an egg, you can probably go either up (add the whole egg) or down (omit the egg completely) without issue.
3. To make soured milk, add 1 1/2 tsp white vinegar or lemon juice to 1/2 cup of regular milk. Let stand 10-15 minutes before using. Be sure to read the FAQ above the recipe card for more tips and ingredient substitution suggestions.
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Hi! I’m Jennifer, a home cook schooled by trial and error and almost 40 years of getting dinner on the table! I love to share my favourite recipes, both old and new, together with lots of tips and tricks to hopefully help make your home cooking enjoyable, stress free, rewarding and of course, delicious!