Lemon Blueberry Sourdough Coffee (Print View)

Moist squares with juicy blueberries, bright lemon zest, sourdough depth, and a crunchy streusel topping.

# Components:

→ Cake Batter

01 - 1/2 cup unsalted butter, softened
02 - 3/4 cup granulated sugar
03 - 2 large eggs
04 - 1/2 cup sourdough starter, unfed or discard
05 - 1 cup whole milk
06 - Zest of 1 lemon
07 - 2 tablespoons fresh lemon juice
08 - 1 teaspoon vanilla extract
09 - 2 cups all-purpose flour
10 - 2 teaspoons baking powder
11 - 1/2 teaspoon baking soda
12 - 1/2 teaspoon fine sea salt
13 - 1 1/2 cups fresh or frozen blueberries

→ Streusel Topping

14 - 1/4 cup unsalted butter, cold and diced
15 - 1/3 cup light brown sugar, packed
16 - 1/2 cup all-purpose flour
17 - 1/2 teaspoon ground cinnamon
18 - Pinch of salt

# Preparation Steps:

01 - Preheat oven to 350°F. Line a 9-inch square baking pan with parchment paper, leaving overhang on sides for easy removal after baking.
02 - In a small bowl, whisk together flour, brown sugar, cinnamon, and salt. Add cold diced butter and rub mixture between fingertips until pea-sized crumbs form. Transfer to refrigerator until ready to use.
03 - In a medium bowl, whisk together flour, baking powder, baking soda, and salt. Set aside.
04 - In a large bowl, beat softened butter and granulated sugar together for 2-3 minutes until light and fluffy. Add eggs one at a time, beating well after each addition.
05 - Stir sourdough starter, milk, lemon zest, lemon juice, and vanilla extract into the butter mixture until combined. The batter may appear slightly curdled.
06 - Add dry ingredient mixture to wet ingredient mixture and fold together until just combined. Do not overmix.
07 - Gently fold blueberries into batter until evenly distributed throughout.
08 - Pour batter evenly into prepared pan. Sprinkle reserved streusel topping in an even layer across the surface.
09 - Bake for 35-40 minutes until a toothpick inserted in the center comes out clean and the top is golden brown.
10 - Cool in pan for 15 minutes. Using parchment overhang, lift cake from pan and transfer to wire rack to cool completely before cutting into 12 squares.

# Expert Advice:

01 -
  • The sourdough starter adds moisture and a gentle tang that makes these squares taste like they've been resting on a Parisian café counter, not your kitchen counter.
  • Blueberries burst with juice when you bite through the crumb, and the lemon zest keeps everything bright instead of heavy.
  • That streusel topping delivers the satisfying crunch that separates a good coffee cake from one people actually remember.
02 -
  • Don't thaw frozen blueberries before folding them in—they'll bleed color and juice into the batter, turning everything purple instead of creating distinct pockets of flavor.
  • The batter will look slightly curdled after you add the sourdough starter, and that's exactly what should happen; it means the acid is doing its job and the cake will be incredibly moist.
03 -
  • Weight your ingredients if you possibly can—it removes the variable of how tightly you pack flour into your measuring cup, which will change your cake's texture more than any other single factor.
  • Cold streusel ingredients are non-negotiable; dice the butter and keep everything in the fridge until you're ready to assemble, because warm streusel melts into the batter instead of staying distinct.
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