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sourdough discard rhubarb cake in a square pan with bowl of whipped cream to the left.

Moist Rhubarb Sourdough Discard Cake

This delicious rhubarb cake is incredibly moist with a light and airy crumb thanks to sourdough discard! The soft texture has rhubarb in each bite, complemented by lemon zest to bring out its flavor.
Author: Amanda Paa
Yield: 1 (8-inch) cake
Prep Time :15 minutes
Cook Time :45 minutes

Ingredients

  • 8 ounces fresh rhubarb, 3/4 of the rhubarb cut into 1/2 inch chunks, and remaining cut into pieces that fit inside the pan diagonally to create a pattern
  • 170 grams all purpose flour
  • 1 1/2 teaspoons baking powder
  • 1/2 teaspoon fine salt
  • 155 grams cane sugar
  • 1/2 cup sunflower or grapeseed oil
  • 1 tablespoon lemon zest
  • 2 eggs, room temperature
  • 3 tablespoons runny honey
  • 65 grams sourdough discard, preferably room temperature
  • 1 1/2 teaspoons vanilla extract
  • 1 teaspoon fresh lemon juice
  • 3 tablespoons whole milk

Equipment

  • 1 8-inch square cake pan

Instructions 

  • Preheat oven to 350 degrees F. Grease and line a square 8-inch cake pan.
  • Add chopped rhubarb to a medium bowl.
  • In another medium bowl, whisk together flour, baking powder, and salt. Scoop 2 heaping teaspoons from this mixture and add it to bowl with chopped rhubarb. Toss to combine (this lightly coats the rhubarb so it doesn't sink in the cake). Set aside.
  • In a stand mixer or with a hand mixer, on medium speed beat 145 grams sugar with the oil and lemon zest for 1 1/2 minutes (this helps to dissolve the sugar). Then add eggs, and beat for 1 minute on medium speed, so that the mixture is frothy.
  • Add honey, sourdough discard, vanilla extract, lemon juice, and milk, and mix on medium speed until just combined. Then add in dry mixture on low speed, just until no bits of flour remain.
  • Gently fold in rhubarb (it's okay if you can see a little flour on the rhubarb when its in the batter.) Place batter into greased and line 8-inch cake pan, and smooth top. Add the longer pieces of rhubarb to the top, in any pattern you'd like. Sprinkle top of cake with 2 heaping teaspoons sugar. Bake for 30 minutes at 350 degrees F, then turn oven down to 330 degrees F and bake for 12-15 minutes more, until toothpick comes out with a few moist (but not wet) crumbs. Remove from oven and let cool on cooling rack.
  • In a sealed container, this cake stores very well in the refrigerator for up to 4 days.