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Oma's Rhubarb Cake

Rhubarb cake in the style of Oma: a moist yellow sheet cake studded with pink rhubarb pieces, then dusted with powdered sugar. Made by macerating rhubarb with sugar for juicy bites and baking until the center is toothpick-clean.
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Prep Time 20 minutes
Cook Time 45 minutes
cooling 30 minutes
Total Time 1 hour 35 minutes
Servings: 12 servings
Course: Dessert
Cuisine: German
Calories: 360
Ingredients Equipment Method Notes

Ingredients
  

Rhubarb mixture
  • 3 cups fresh rhubarb, diced
  • 0.5 cup sugar (for rhubarb)
Cake batter
  • 2 cups all-purpose flour
  • 1.5 cups sugar for creaming
  • 0.5 cup butter, softened
  • 2 eggs
  • 1 cup buttermilk
  • 1 tsp vanilla extract
  • 1 tsp baking soda
  • 0.5 tsp salt
To finish
  • 1 powdered sugar for dusting

Equipment

  • 1 sheet pan

Method
 

Macerate the rhubarb
  1. Toss diced rhubarb with 1/2 cup sugar and set aside to macerate for 15 minutes, until glossy and juicy. Visual cue: rhubarb will look wetter as sugar dissolves.
Prepare and bake
  1. Preheat oven to 350°F and grease a 9x13-inch baking pan. Visual cue: pan is coated so the cake releases cleanly.
  2. Cream together softened butter and 1 1/2 cups sugar until light and fluffy. Visual cue: mixture turns pale and increases in volume.
  3. Beat in eggs and vanilla extract until smooth. Visual cue: batter becomes cohesive and glossy.
  4. Combine all-purpose flour, baking soda, and salt in a separate bowl. Visual cue: dry mix looks evenly speckled.
  5. Add the dry ingredients to the butter mixture alternating with buttermilk, mixing until just combined. Visual cue: stop mixing once no dry flour remains.
  6. Fold in the sugared rhubarb and pour batter into the prepared pan. Visual cue: pink rhubarb pieces are evenly distributed.
  7. Bake at 350°F for 40-45 minutes until a toothpick inserted in center comes out clean. Visual cue: top looks set and springy without wet batter.
Cool and serve
  1. Cool the cake completely for 30 minutes. Visual cue: center firms up and the pan can be handled safely.
  2. Dust with powdered sugar and serve. Visual cue: a light white layer sits on top of the moist yellow crumb.

Notes

Pro tip: macerate the rhubarb for the full 15 minutes so it releases juices that keep the cake moist. Store covered in the fridge up to 3 days (best texture within 48 hours); freeze the cooled cake up to 2 months. For a dietary swap, replace buttermilk with an equal amount of dairy-free buttermilk (or use plant milk plus a tablespoon of acid) for a lactose-free version.