Preheat oven to 325F and grease a 9" springform pan.
In a medium bowl, whisk the eggs. Mix in the sour cream, vanilla, lemon zest, and lemon juice. Slowly add the melted butter, whisking to combine.
3 large eggs, 1 cup sour cream , 1 tsp vanilla extract, zest and juice of 1 lemon, ½ cup (114g) unsalted butter
In a large bowl, toss together the flour, sugar, baking powder, and salt. Make a well in the center and add the wet ingredients. Stir until just combined.
2½ cups (315g) all-purpose flour, 1 cup (200g) granulated sugar, 1 Tbsp baking powder , ½ tsp salt
Spread half the batter evenly into the prepared pan. Arrange half of the blackberries on top.
2 cups blackberries
Repeat with the remaining batter and blackberries. Sprinkle with more sugar on top.
1 Tbsp granulated sugar
Bake for 60-70 minutes or until a toothpick inserted into the center comes out clean.
Notes
Leftovers can be stored in an airtight container at room temperature for up to 2 days, or refrigerate for up to 5 days. Bring to room temp before serving for the best texture.