strawberry rhubarb buttermilk upside-down cake

Oh, hi!


Weird.  Looks like we actually have a recipe today.  Unlike what I made yesterday and a recipe I made last week that never made it to this space. 


When you make a recipe and have to taste test it 15 times to figure out if it’s just “okay” or “really good” that probably means it’s just “okay.”

When you make a recipe and “taste test” 15 bites because you just can’t stop, what you have is definitely “really good.”

You with me?


After 2 recent flops I was on pins + needles waiting for this cake to bake.  I thought it was going to be a disaster from the start.  Way to be optimistic, huh?

The idea sounded doable but I wasn’t really sure how much fruit to put in the pan, how liquefied it would end up, and then if the cake would actually bake on top of it.


I cooked the fruit + sugar mixture and it was way juicier than I was thinking it should be, but I kept on with the plan.

I poured the batter overtop and thought, that doesn’t look like enough.  Ahh!  But in the oven it went.

I turned the oven light on about 10 times to check the progress.  When I saw the filling bubble around the sides I thought this cake was done for.  I figured the batter + filling fully mixed together and there would just be a slight crusty layer of cake.


And then the cake was done.  The toothpick told me so!

And then came the next question.  Do I flip this sucker out of the pan for a true upside-down cake, or do I just slice + serve straight from the pan.

I decided to take my chances even though I knew there was no 2nd trial in the future if this didn’t work.  I was out of strawberries and didn’t have our car to run out for more.

The plate covered the pan, then a quick flip, and…nothing.  No cake!


But after about 10 seconds I heard a nice “thud!”


It came out!  In one piece!  But how did it taste??  Cakes are tricky because you kind of need to wait for the photo shoot to be complete before giving it a taste test.

Or, you can chow down on one side of the cake and hide it from the photos as seen below.  This is the side you can’t see 2 photos up!

And this is when I realized after the 15th “taste test” that this cake was “really good!” 

As in, I could not stop eating it.


Photo.  Bite.  Photo.  Bite.


Totally edible.


With a tangy fruit topping, a lightly sweetened cake, and a hint of vanilla, this is my dream summer dessert.  A little bit of all the things I love!

Note: This cake is not a light + fluffy cake.  It’s quite thick but moist and holds up well to the gooey fruit topping.


Print this!

Strawberry Rhubarb Buttermilk Upside-down Cake

gluten-free // yields 1, 10-inch cake

Rhubarb Mixture:

  • 1 1/2 cups chopped rhubarb, 1/4-inch slices
  • 1 1/2 cups quartered strawberries, hulled
  • 1/4 cup muscovado sugar, lightly packed
  • 2 tablespoons honey
  • 2 tablespoons butter
  • 2 teaspoons arrowroot starch
  • 1 vanilla bean pod, seeds scraped + reserved for cake


  • 1/2 cup + 2 tablespoons gluten-free oat flour
  • 1/2 cup + 2 tablespoons blanched almond flour
  • 1/4 cup + 2 tablespoons muscovado sugar, lightly packed
  • 1/3 cup sweet rice flour
  • 1 teaspoon baking powder
  • 1/2 teaspoon salt
  • 2 eggs
  • 1/3 cup buttermilk
  • 3 tablespoons unsweetened applesauce
  • 2 tablespoons butter, melted + slightly cooled
  • beans from 1 vanilla bean pod, ~1/4 teaspoon

*Have all cake ingredients out + ready to go, so you can whip up the cake while the rhubarb mixture cools.

  1. Heat butter in a 10-inch cast iron skillet over medium heat. 
  2. Once melted, swirl butter around the sides of the pan.
  3. Add the rhubarb, strawberries, sugar, honey, starch, and empty vanilla bean pod.
  4. Stir together and let simmer/low-boil for 8-10 minutes until the fruit is very tender.  Stir a few times while cooking. The mixture will be very wet.  [refer to photo 2]
  5. Remove from the heat and let cool for 10-12 minutes.
  6. Preheat your oven to 350* F.
  7. In a large bowl, stir to combine the oat flour, almond flour, sugar, sweet rice flour, baking powder, + salt.
  8. In another bowl whisk the eggs and then vigorously whisk in the buttermilk, applesauce, melted butter, and vanilla beans. 
  9. Pour the wet into the dry and whisk together until just combined. 
  10. Pour evenly overtop of the rhubarb mixture and lightly spread to the edges if needed.
  11. Bake for 25-30 minutes until set, cracked, and a toothpick comes out clean.  [refer to photo 3]Be careful not to poke all the way through to the gooey rhubarb mixture.
  12. Let cool for 15-20 minutes and slide a knife around the edge of the pan to loosen the cake. 
  13. Place a large plate upside-down over the pan then, holding the plate and pan together flip them so the plate is sitting on its bottom.  Give a light shake of the pan until you hear it fall onto the plate.  Mine took about 5-10 seconds to drop but it came out fully clean from the pan.
  14. Let cool for at least 15 minutes for the topping to set/thicken + the cake to firm, then serve warm or fully cooled with whipped cream or a side of vanilla ice cream.

notes/substitutions:  Coconut oil can be subbed for butter and non-dairy buttermilk can be used instead of real buttermilk to make this dairy free.  Non-dairy buttermilk: Stir 1 teaspoon vinegar with 1/3 cup unsweetened soy/almond/rice milk and let sit for 5-10 minutes.  Brown sugar, sucanat, or coconut sugar can be substituted for muscovado.  If you don’t have vanilla beans, add 1/2 teaspoon vanilla extract to the rhubarb mixture and 2 teaspoons vanilla extract to the wet cake ingredients.  If you can’t tolerate oat flour, sub a high quality gluten-free all purpose blend for oat flour at a 1:1 ratio.

Recommendations for other pans: You could cook the fruit mixture in a skillet then transfer to a 10-inch, greased spring form pan and proceed with the recipe from there.  I can’t say for sure if a regular round cake pan will work.  You may want to line it with parchment to be safe.  If making in an 8-inch pan you’ll need to reduce the amount of fruit/sugar you use slightly and the cake bake time will increase.


Cake.  Win.