Ingredients:

  • 150g granulated sugar
  • 2 tbsp fresh lemon zest
  • 115g unsalted butter, melted and cooled
  • 250g all-purpose flour
  • 2 tsp baking powder
  • 1/2 tsp fine sea salt
  • 2 large eggs, room temperature
  • 240g full-fat sour cream
  • 1 tsp vanilla bean paste
  • 300g fresh or frozen blueberries
  • 65g all-purpose flour (for streusel)
  • 50g brown sugar
  • 45g cold unsalted butter, cubed
  • 1/2 tsp cinnamon

Instructions:

  1. In a large bowl, combine the 150g granulated sugar and 2 tbsp lemon zest. Use your fingertips to rub the zest into the sugar for about 2 minutes until the sugar is fragrant and damp. This step is non negotiable! The friction releases the lemon oils, ensuring the flavor is baked into the sugar rather than just sitting on top of it.
  2. Whisk in the 115g of melted and cooled butter into the lemon sugar. Add the 2 large eggs one at a time, whisking vigorously after each addition until the mixture looks glossy and smooth. Stir in the 240g of sour cream and 1 tsp vanilla bean paste. Note: Room temperature eggs emulsify much faster with the fat, preventing the batter from breaking.
  3. In a separate bowl, whisk together the 250g flour, 2 tsp baking powder, and 1/2 tsp salt. Gradually fold the dry ingredients into the wet mixture using a spatula. Stop until just a few streaks of flour remain. Over mixing at this stage will activate the gluten and make your cake tough.
  4. Take your 300g of blueberries and toss them with 1 tablespoon of flour (taken from the original 250g). Gently fold the berries into the batter. Use a light hand until the berries are evenly distributed but not crushed.
  5. In a small bowl, mix the 65g flour, 50g brown sugar, and 1/2 tsp cinnamon. Add the 45g of cold, cubed butter. Use your fingers to pinch the butter into the dry ingredients until you have a crumbly, clumpy mixture. It should look like coarse wet sand with some larger pebbles.
  6. Grease your pan and pour in the batter, smoothing the top with a spatula. Sprinkle the streusel evenly over the entire surface. Bake at 350°F (175°C) for 45 minutes until a toothpick inserted in the center comes out clean or with just a few moist crumbs.
  7. Let the cake cool in the pan for at least 20 minutes before attempting to slice it. This allows the internal structure to set. You should see the edges pulling away slightly from the sides of the pan, which is a perfect sign of doneness.