Rhubarb & Buckwheat Crumb Cake
Because Rhabarberbuchweizenstreuselkuchen is a mouthful.
Ahh, rhubarb. The first “fruit” of the year. After a long, cold (or only sort-of-cold this year) winter, we're greeted with sour celery and asked to put it in desserts, which is great because I love rhubarb.
The flavor in rhubarb stalks comes mostly from malic acid, giving it a tangy flavor with practically no sweetness. You must add some sort of sugar to rhubarb to turn it into a dessert. I can find ten dozen ways to use rhubarb and not be sick of it.
During my two-week stint at German Bread School, a tray of Kuchen would appear each afternoon. These slices of Kuchen, with either a bread-like base or something more cake-y, usually included some sort of fruit and/or streusel. There was Apfelkuchen, Kirschkuchen, Pfirschkuchen, Chocokirschkuchen, and a few versions of Rhabarberkuchen. I offer the most heartfelt thank you to the bakers who made our daily Kuchen.
The Germans embrace rhubarb just like the Midwesterners do. Come late spring, it sprouts up in farmers' markets and most bakeries. I ate a lot of rhubarb-based bakes in Germany.
The rhubarb at German markets tended to be a bit less red than ours. While we're on the subject, the color of rhubarb doesn't really matter. I tasted tested rhubarb desserts in Germany, and the green ones were as flavorful as the red ones. However, I concede that the ruby-red rhubarb looks resplendent.
In a related matter: You know that I spread the good word of buckwheat whenever I can. When I learned rhubarb and buckwheat are related, I couldn't shut up about it. I still can't. So naturally, I'd pair the two in a recipe.
More and more bakers are hopping aboard the buckwheat train, including one of my favorite food writers (and fellow Tent-baker), Ruby Tandoh.
On to the recipe!
Rhubarb & Buckwheat Crumble Cake
Otherwise known as Rhabarberbuchweizenstreuselkuchen.
As I mentioned last week, y'all need to get familiar with the song “Barbaras Rhabarberbar,” and the Rhabarberkuchen mentioned therein.
I love the Germans' penchant for smushing words together to form mile-long words. In English, we'd call this Rhubarb and buckwheat Crumb (or Crumble) Cake. In German, it might be Rhabarberbuchweizenstreuselkuchen.
Rhabarber [rhubarb] buchweizen [buckwheat] streusel [crumble] kuchen [cake]. Honestly, it would probably be something shorter like Rhabarberkuchen mit Streusel or Rhabarber-Streusel-Kuchen. Nevertheless, it's glutenfrei und lecker [gluten-free and delicious].
Whatever it’s called, here is a one-bowl, stir-together, no-special-tools, whole-grain, gluten-free recipe that brings together earthy, healthy buckwheat with zippy rhubarb. The beaten egg white in the crumble/streusel helps it bake up crunchy, even with the water from the rhubarb below.
My husband says we can't have cake for breakfast, but this hearty, not-too-sweet cake sits perfectly next to a bowl of morning yogurt and a cup of hot coffee.
Makes one 9-inch square cake, about 9-16 servings.
Crumble (AKA Streusel)
200 g buckwheat flour
80 g sugar
3/4 teaspoon fine sea salt
113 g (1 stick) unsalted butter, melted
1 teaspoon vanilla extract
1 egg white
2 tablespoons whole buckwheat groats
Rhubarb
400 g rhubarb, trimmed
1 Tablespoon sugar (or 1 Tablespoon vanilla sugar, yum!)
1 Tablespoon buckwheat flour
1/8 teaspoon fine sea salt
Cake
180 g sugar
1/2 teaspoon fine sea salt
180 g buckwheat flour
60 g almond flour
2 teaspoons baking powder
100 g (7 Tablespoons) unsalted butter, melted
30 g (3 Tablespoons) olive oil (or any neutral-flavored oil)
3 large eggs, room temperature
2 teaspoon vanilla extract
80 g Greek-style yogurt (full-fat is best, but any will do)
Butter a 9-inch by 9-inch square metal baking pan* and line it with parchment paper. My buddy Adam has a great tip for lining square pans. I adhere to this method to prevent madness.
Make the crumble top: Whisk together the buckwheat flour, sugar, and salt. Add the vanilla extract to the melted butter and stir. Pour the butter mixture into the dry ingredients. Stir to combine until it starts to form clumps. Get in there with your hands to finish stirring and squeeze some of the mixture into bigger clumps. Refrigerate until needed. (You can make this part up to a day ahead of time.)
Wash the rhubarb, dry it, then chop it into 1/2-inch chunks, set it aside in a bowl
In a large mixing bowl, add the sugar, salt, buckwheat flour, almond flour, and baking powder. Whisk it all to combine. Add the melted butter, olive oil, beaten eggs, vanilla extract, and Greek yogurt, then whisk to thoroughly combine (no lumps, please!). There's no gluten here, so you can't over-mix. Pour the batter into the prepared pan and spread it into an even layer
Toss the chopped rhubarb with 1 Tablespoon sugar, 1 Tablespoon buckwheat flour, and a pinch of salt. Evenly distribute the rhubarb on top of the cake batter. Sprinkle any leftover sugar or flour on top of the rhubarb. Do not push the rhubarb down; let it sit on the top as much as possible.
Beat one egg white with a fork until foamy, and stir this gently into the streusel mixture. Get in there with your hands and toss the egg white thoroughly. Squeeze the mixture together so that there are some bigger chunks. Sprinkle the streusel evenly on top of the cake. Shower on the buckwheat groats for some added crunch.
Put the cake on the middle rack of the oven and bake at 350F for 50-60 minutes until it feels quite firm when pressed in the center and a toothpick inserted in the center comes out with just a few crumbs attached (no wet batter). Let cool for at least 30 minutes in the pan before serving.
This cake is best the day it's made or the following day.
*I adore this removable-bottom pan from Fat Daddio's because I can get the cake out of the pan without losing any crumble. This is not a sponsored post…but it could be ;-)
Happy Baking,
Martin
I’m such a fan of rhubarb I bought some in the freezer section at a local grocer. Buckwheat flour is always in my pantry. Can’t wait to bake this and have it for breakfast!! Thanks for sharing this recipe.
PS, I would love more tips on baking tools you find indispensable. Especially springform pans! And yes, those should be sponsored ;) as long as they are sincere! Yhe certified Sorge seal of approval would be enough for me!