Ingredients:

  • 150g light brown sugar, packed
  • 125g all-purpose flour
  • 115g unsalted butter, cold and cubed
  • 5g ground cinnamon
  • 2g fine sea salt
  • 250g all-purpose flour
  • 200g granulated sugar
  • 10g baking powder
  • 3g baking soda
  • 3g salt
  • 240g full-fat sour cream, room temperature
  • 115g unsalted butter, melted and cooled
  • 2 large eggs, room temperature
  • 10ml pure vanilla extract
  • 150g fresh blueberries
  • 150g fresh peaches, sliced into 1/2-inch segments
  • 15g all-purpose flour for dredging

Instructions:

  1. Preheat oven to 350°F (180°C). Grease a 9x13 inch pan thoroughly.
  2. Construct the Streusel: Combine 150g light brown sugar, 125g flour, 5g cinnamon, and 2g salt. Cut in the 115g cold cubed butter using a pastry cutter or your fingers until it resembles coarse, pea sized crumbs. Place in the fridge.
  3. Prepare the Fruit Barrier: Gently toss the 150g blueberries and 150g peach segments with 15g of flour until every piece is matte and dusty.
  4. Whisk Dry Ingredients: In a large bowl, sift together 250g flour, 200g granulated sugar, 10g baking powder, 3g baking soda, and 3g salt.
  5. Emulsify Wet Ingredients: In a separate bowl, whisk 240g sour cream, 115g melted (and cooled!) butter, 2 eggs, and 10ml vanilla until the mixture is silky and pale yellow.
  6. Combine with Care: Pour the wet mixture into the dry. Use a spatula to fold gently until no streaks of dry flour remain. The batter will be very thick — this is intentional.
  7. Layer the Foundation: Spread half of the batter into the prepared pan. Scatter half of the floured fruit over the top.
  8. Final Assembly: Dollop the remaining batter over the fruit, then top with the rest of the peaches and berries. Finish by blanketing the entire surface with the chilled streusel.
  9. Bake for Gold: Slide into the oven for 45 minutes. Note: Test the center with a wooden skewer; it should come out with a few moist crumbs but no wet batter.
  10. The Cooling Mandate: Let the cake sit in the pan for at least 20 minutes before slicing. The residual heat finishes setting the center.