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sourdough strawberry rhubarb upside-down cake sitting on a vintage cake stand on a tea towel on the counter top.

Sourdough Strawberry Rhubarb Upside-Down Cake

A seasonal upside-down cake, using spring strawberries and rhubarb caramelized in maple sugar and butter to create a gut-friendly indulgence.
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Servings 8

Ingredients
  

  • 1 Cup Rhubarb About 2 stalks, sliced ½" thick
  • 1 Cup Strawberries Stems trimmed, halved
  • 1/4 Cup Butter Half Stick
  • 1 Shot Dark Rum
  • 3 1/2 Cups Sourdough Starter active or discard
  • 1 Egg
  • 1 tsp. Salt
  • 1/4 tsp. Ground Cardamom
  • 1/2 Cup Maple Sugar
  • 1 stick or 1/2 Cup Butter
  • 1/4 Cup Milk the amount you use may vary depending on the thickness of your sourdough starter.
  • 1-1/2 tsp. Baking Powder

Instructions
 

  • In a small saucepan or skillet place one stick of butter over medium-low heat to brown the butter.
    When the butter has browned, set aside to cool for 10 minutes.
  • Preheat the oven to 400 degrees Fahrenheit, and preheat the cast iron skillet on the stovetop over low heat.
  • Prepare the fruit by chopping the rhubarb into 1/2" slices removing the stems from the strawberries, and cutting them in half.
  • Get 1/4 cup of butter in the cast iron skillet and turn the heat up to medium-low. When butter has fully melted, stir in brown coconut sugar, and a shot of dark rum. Mix with a whisk constantly for one minute while the sugar dissolves and the mixture bubbles to create a caramelized pan of goodness.
  • Remove from the heat and spread rhubarb and strawberry slices in a layer over the sugar mixture, completely covering the mixture. Set aside.
  • In a mixing bowl combine sourdough starter, cardamom, salt, maple sugar, and an egg until fully incorporated.
  • Next, add the cooled brown butter, and 1/4 cup of cold milk.
  • Add Baking Powder, and mix thoroughly.
  • Pour the batter over top of the rhubarb and strawberry slices in the skillet; spread evenly to cover.
  • Bake in preheated oven until the cake begins to bubble around the edges and the top is golden brown. Add a toothpick in the center to see if it comes out clean. 30-35 minutes.
  • Cool inside the skillet on the counter for 30 minutes.
  • After the cake has cooled, place a cutting board on top of the skillet invert the cake by flipping it over onto the cutting board. The skillet should come out clean.
  • Transfer the cake onto a cake plate or pedestal and decorate.
  • Bon Appétite!

Notes

  • You want the batter to be the thickness of the pancake batter. You can adjust the thickness of the batter with a little more or a little less milk. It all depends on the consistency of your starter. 
  • If the cake doesn't immediately come out of the skillet, run a knife around the edge of the pan to loosen it, and try again. 
  • I used strawberries and rhubarb, but this cake works well with many different seasonal berries and stone fruits.