Martha’s Rhubarb Upside Down Cake is my regular recipe to make with rhubarb. What starts out as a streusel topping becomes the crumbly bottom with a stunning mosaic rhubarb top! This deliciously sweet, tart and a delightfully spongy cake is notable served slightly warm with whipped cream or vanilla ice cream!

One day I’d love to meet Martha Stewart. Maybe she will have me on her show? Does she still have a show? And if not what happened? But if she still does where can I find it??

First thing I would tell her would be how much A regular here this cake.

She surely knew what she was doing when she came up with the recipe for this Rhubarb Upside Down Cake. It’s my go-to recipe to use the rhubarb from my garden. There’s a lot of butter and sugar going on in this cake, but I personally believe that all things in moderation. Plus there’s rhubarb in it so it’s basically healthy right? (lie to me)

I only made a few tweaks on her recipe, like reducing the flour and adding a little vanilla and more orange zest into the cake batter. Nothing major but does make all the difference.

The rhubarb in this cake is tart and flavor-packed which is a great contrast to the sour cream cake that is soft, spongy and with a subtle tang. The crumble topping adds a flavor-packed texture. The dessert as a whole is a winner.

To Make Martha’s Rhubarb Upside Down Cake Gather:

for the crumble topping:

unbleached all-purpose flour – The base of the crumb mixture.
granulated sugar – For sweetness and crunch.
kosher salt – This balances the sweetness.
unsalted butter – This is what binds the crumble mixture together.

the rhubarb:

fresh rhubarb – Sour and tangy once baked.
granulated sugar – This is needed to balance the tang of the rhubarb and draw out the liquids.

for the cake:

unbleached all-purpose flour – Provides the structure for this cake recipe.
baking powder – Reacts with the heat to give a leavening boost while the cake is in the oven.
kosher salt – For flavor and balancing sweetness.
unsalted butter – Adds flavor, moisture, gives this cake a soft texture and aids in leavening.
granulated sugar – Besides sweetness, it also adds flavor, bulk, and structure.
orange zest – Adds bright citrusy notes.
fresh orange juice – For moisture and flavor.
real vanilla extract – Enhances all the other flavors in the recipe.
eggs – Provide structure, leavening and add richness, color, and flavor.
sour cream – Will make the cake moist and rich.

Make the Crumb Topping:

In a medium mixing bowl, measure and add 1/2 cup flour, 1/4 cup sugar, 1/8 teaspoon of kosher salt and pour in 1/4 cup (4 tablespoons) melted butter.

crumb topping in clear bowl.
Stir together until large clumps form, and set aside.

PREPARE The Rhubarb:

Take 1 pound of fresh rhubarb and give it a good scrub and pat dry, then trim off the rough or dried ends and discard.

Holding your knife at a sharp angle, make slices about a half an inch thick working your way down the stalk. It doesn’t have to be precise, but surely keep those little end bits too because they’re good for filling in the small empty spaces.

Throw the sliced rhubarb in a large mixing bowl with 3/4 cup sugar.

Stir and let them sit. The sugar will pull the juice out of the rhubarb.

Generously grease a 9-inch pie pan with nonstick spray. Dice a 1/2 stick of butter in to pieces and then drop it into the pan.

Lay the sliced rhubarb on its side making a mosaic like pattern, using the dots of butter to hold them in place. I think Martha simply dumps her rhubarb in, and you could do that too if you wish, however I think this looks way prettier!

Keep going and use the smaller pieces to fill in the gaps. Spoon a little (not all) of the rhubarb sugar over top or don’t. This step is optional.

For The Cake Batter:

In a large mixing bowl, whisk together 1 cups flour, 1-1/2 both teaspoons baking powder and kosher salt until combined.

Add 1 softened stick (8 tablespoons) of butter (I know more butter) and 1 cup sugar into a large mixing bowl.

Cream the butter and sugar on medium speed until light in color and fluffy.

Meanwhile quickly grate 1 teaspoon orange zest and add it to the butter/sugar mixture.

Juice 1 tablespoon of fresh orange juice and add that in as well.

Add in a teaspoon of vanilla extract and mix on low speed until combined.

Next add in 2 eggs, one at a time until mixed thoroughly, scraping down the sides in between.

Then alternately add a spoonful of the dry ingredients…

Alternate adding a spoonful at a time of the (1 cup) sour cream, until all ingredients are incorporated.

This cake batter smells like citrus, vanilla with a sour cream tang. So. Good.

Pour the batter over top of the rhubarb and spread evenly with an offset spatula.

Sprinkle the crumb topping over top, breaking any extremely large clumps into smaller ones.

This crumb topping will eventually become the bottom. swoon.

Place on a rimmed metal baking sheet and slide onto the middle rack in your preheated 350° oven and bake for 45 to 55 minutes. Or until a toothpick inserted into the center comes out clean and the cake top sort of springs back when touched. In my teeny hotbox of an oven it is closer to 45 minutes.

The rhubarb will bubble and may spill over, luckily the sheet pan will catch it and not dirty the bottom of your stove. Remove and let cool for ten minutes.

Once it has cooled for the ten minutes; run a knife around the edge of the cake to loosen.

Invert on to your regular platter or cake stand and let cool completely.

I wasn’t getting the pictures I wanted indoors, the lighting in my kitchen was weird that day and it wasn’t doing this cake any justice what-so-ever.

So I sliced me a sliver and took it outside and then… the color popped!

This cake is deliciously dessert-y and yet the leftovers are dependable for a late breakfast or brunch alongside a steaming cup of tea or coffee. The crumble bottom adds a surprising texture to this savory spongy cake. And of course the rhubarb is everything.

It truly is heaven on a plate.