Ingredients:

  • 1/2 cup (115g) unsalted butter, softened
  • 3/4 cup (150g) granulated sugar
  • 2 large eggs, room temperature
  • 1 1/2 cups (190g) all-purpose flour
  • 1 tsp baking powder
  • 1/4 tsp salt
  • 4 cups (500g) fresh rhubarb, chopped into 1/2-inch pieces
  • 1 tbsp cornstarch
  • 2 tbsp granulated sugar
  • 1 cup (240g) full-fat sour cream, room temperature
  • 1 large egg
  • 1 tsp vanilla extract
  • 2 tbsp granulated sugar
  • 3/4 cup (95g) all-purpose flour
  • 1/2 cup (100g) granulated sugar
  • 6 tbsp (85g) cold unsalted butter, cubed
  • 1 tsp ground cinnamon
  • 1/2 cup (115g) unsalted butter

Instructions:

  1. Wash and pat the chopped rhubarb completely dry. In a bowl, toss the rhubarb with 1 tablespoon of cornstarch and 2 tablespoons of sugar until evenly coated to prevent sogginess.
  2. In a medium mixing bowl, cream the 115g softened butter and 150g sugar with an electric mixer until pale and fluffy. Beat in 2 eggs one at a time. Gently fold in 190g flour, baking powder, and salt. Spread the thick batter into a greased and lined 9-inch springform pan.
  3. Scatter the prepared rhubarb over the cake batter. In a separate bowl, whisk together the room temperature sour cream, 1 egg, vanilla extract, and 2 tablespoons of sugar until smooth. Pour this custard over the rhubarb layer.
  4. In a small bowl, combine 95g flour, 100g sugar, 85g cold cubed butter, and cinnamon. Rub with your fingertips until pea-sized clumps form. Sprinkle the streusel over the custard layer.
  5. Bake at 350°F (175°C) for 45–50 minutes until the edges are golden-brown and the center is stable with a very slight jiggle.