A delicious rhubarb dessert, this rhubarb pie cake combines a rhubarb filling in a buttermilk biscuit dough. You can use fresh rhubarb or frozen rhubarb and since it uses a lot, it’s a great way to use your Spring rhubarb crop!
So just to be clear, what we have here is a buttermilk biscuit dough, rolled and filled like a pie, but is really a rhubarb biscuit cake. Whatever you call it though, this rustic rhubarb pie is wonderfully delicious and a nice change from a conventional rhubarb pie.
This is the rhubarb recipe to make when you have a lot of rhubarb to use up, as it uses 5 cups of diced rhubarb for the filling!
Ingredients and substitutions
A few notes about the key ingredients …
Rhubarb – You can use fresh rhubarb or frozen rhubarb here. If frozen, measure out before thawing, then allow the rhubarb to thaw in a colander, allowing the extra moisture to drip off. Pat dry before proceeding. You’ll need about 5 cups of diced rhubarb, but if you find yourself a little short of rhubarb, I don’t think you can go wrong topping it up with some diced strawberries.
Buttermilk – Real buttermilk is always best if you have it. If not, make your own buttermilk by combining 1 cup milk with 1 Tbsp lemon juice or white vinegar and letting stand 10 minutes. If that isn’t an option, you can just use milk here without issue.
You will also need – all-purpose flour, baking soda, salt, white sugar, butter, and egg (1).
How to make rhubarb pie cake
This is a quick visual summary of the process of making this recipe. Always refer to the complete instructions in the Recipe Card below when making the recipe.
The dough starts by cutting butter into the flour mixture. You can do this with a pastry cutter, or simply rub it in with your fingertips. You want an even crumb with pea-sized butter pieces. Add the buttermilk/egg mixture a bit at a time, stirring as you go and adding only as much liquid as you need to moisten all the flour. You may not need all of it (or you may need a splash more).
You are aiming for a moist, but not sticky dough. Remove the dough to a work surface and knead gently a bit, adding a bit of flour, if necessary, then divide the dough into 2 pieces.
Roll one piece of the dough into a roughly 10-inch circle and place into a greased pie plate. Prepare the rhubarb filling by combining the diced rhubarb with the sugar/flour mixture. Add to the pie plate. Roll the second piece of dough and place on top. Brush with buttermilk and sprinkle some white sugar over top. Cut some slits in the top and bake!
Recipe tips!
- The 1 cup of sugar added to the rhubarb is what I would consider as a minimum for rhubarb. It will allow a little of the rhubarb tartness to shine through. If you prefer a sweeter rhubarb experience, add the extra 1/4 cup of sugar.
- When mixing the biscuit dough, add only as much of the buttermilk as you need to create a moist, but not sticky dough. You may not need to use all of it or you may need a splash more.
- Don’t hesitate to add a sprinkling of flour when rolling if the dough is sticking at all. Work quickly though, so the butter in the dough doesn’t warm too much.
- Be sure to bake for 50 minutes, to ensure that the rhubarb is nice and soft. You may need to cover the top loosely with a sheet of aluminum foil if it is nicely browned before that. Then allow to continue baking.
- This cake will have some liquid in it after baking, especially when made with fresh rhubarb. The bit of sweet rhubarb juice soaks nicely into the biscuit crust in a cobbler kind of way, so just spoon it over or under a slice and enjoy.
- To serve, you can slice this one like a pie or just spoon it out, if you prefer.
- This cake is best enjoyed within 24 hours of baking. While it will still be fine beyond that point, the biscuit will continue to absorb liquid from the fruit and become quite moist.
Making ahead, storing and freezing
This rhubarb pie cake is best enjoyed on the day it is baked. Store leftovers in an airtight container for another day or so or freeze up to 3 months for longer storage.
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Get the Recipe: Rustic Rhubarb Pie Cake
Ingredients
Biscuit dough:
- 2 3/4 cups all-purpose flour
- 1 teaspoon baking soda
- 1/4 cup granulated white sugar
- Pinch salt, add a bit more if using unsalted butter
- 1/3 cup butter, cold, salted or unsalted, cut into 6 pieces
- 1 large egg
- 3/4 cup buttermilk, or milk *see Note 1
Filling:
- 4 1/2 – 5 cups rhubarb, fresh or frozen, diced *see Note 2
- 2 Tablespoons all purpose flour
- 1 – 1 1/4 cups granulated white sugar, *see Note 3
For topping:
- Additional buttermilk, for brushing top before baking
- Additional granulated white sugar, for sprinkling top before baking
Instructions
- Preheat oven to 350F (regular bake/not fan-assisted) and lightly grease a 10-inch deep dish pie plate.
- Prepare the rhubarb and set aside in a large bowl.
- In a large bowl, whisk together the flour, baking soda, sugar and salt. Add the chunks of butter and using your fingertips, cut or rub the butter into the flour mixture, until you have an even crumb, with pea-sized pieces of butter.
- In a small bowl, whisk together the egg and buttermilk and gradually add this to the flour mixture, adding the last part in small increments and adding only as much as you need until a moist (but not sticky) dough is formed. Remove dough to a lightly floured surface and knead lightly. Divide dough into two equal pieces. Roll one half into a roughly 10-inch circle and use it to line the bottom of the pie plate.
- In a small bowl, combine the white sugar for the filling with the flour for the filling. Add to the bowl with the rhubarb and toss to combine. Pour the rhubarb on top of the bottom crust. Set aside.
- Roll the second piece of dough for the top. Brush the edge of the bottom dough with water, then place the top piece on and press lightly around the edges to seal. Brush the top with additional buttermilk (or milk), then sprinkle with white sugar. Cut several slits in the top to allow the steam to escape (make sure your slits are deep enough to reach the fruit layer).
- Place the pie plate onto a baking sheet (to catch bubble-overs) and bake in a preheated oven for 45-55 minutes, or until the crust is golden browned and the fruit is tender and bubbling. (I generally bake for about 50 minutes with fresh rhubarb.) *If the top is at risk of over-browning, loosely cover it with a sheet of aluminum foil for the last part of baking. I suggest checking at about 40 minutes. I usually have to cover at about 45 minutes for the last 5-8 minutes of baking.
- Remove from oven and allow to stand at least 15 minutes before eating, to allow the filling to set a bit. Serve warm with a scoop of vanilla ice cream, if you like.
Notes
More rhubarb recipes to love!
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!
Would it work to cook the rhubarb down a little before assembling the cake? Maybe there wouldn’t be as much liquid that way?
Hi Alice, I’ve had good luck with just letting the frozen rhubarb thaw in a strainer and letting the excess moisture drain off. Then I dump it on some paper towel to dry off a bit more. I know you can see some liquid in the photos, but trust me, it isn’t excessive. That said, you won’t hurt it by pre-cooking it a bit. If you try it, let me know how it works out.
I have yet to grab some rhubarb, but now I know what I’ll be making first Jennifer! This cake looks delicious!
Thanks Mary Ann :) I couldn’t resist a little rhubarb baking, so I sought some out, even though it’s early yet for my garden rhubarb here.