Coffee cake with sour cream and blackberries

Ingredients:

Pie

• 8 tbsp (110 g) unsalted butter, room temperature, plus extra for greasing the pan
• 2 cups premium flour
• 1 teaspoon baking powder
• 0.5 tsp of soda
• 0.5 tsp fine salt
• 1 cup granulated sugar
• 2 large eggs
• 2 tsp vanilla extract
• 1 cup sour cream
• 1.5 cups fresh blackberries

Streusel

• 3/4 cup flour
• 2/3 cup firmly packed light brown sugar
• 1 teaspoon ground cinnamon
• A pinch of fine salt
• 70 g unsalted butter, room temperature

Preparation:

1. In a small bowl, combine the flour, brown sugar, cinnamon, and salt. Add the butter and mix thoroughly with your fingers or a fork until all the butter is evenly distributed and incorporated into the flour. Form small to medium-sized clumps with your fingers.
2. Preheat oven to 175°C. Grease a 20cm square baking pan with butter.
3. In a medium bowl, whisk together flour, baking powder, baking soda and salt.
4. In a large bowl, beat the butter and sugar with a mixer on medium speed until light and fluffy, about 3 minutes. Add the eggs, one at a time, beating well after each addition. Stir in the vanilla extract.
5. Reduce mixer speed to low and add the flour mixture in 3 additions, alternating with the sour cream, beginning and ending with the flour. Mix only until all ingredients are incorporated.
6. Spoon half the batter (it will be very thick) into the prepared pan and smooth it out with an offset spatula. Sprinkle with blackberries. Then spoon in the remaining batter and smooth the surface. Sprinkle with streusel.
7. Bake until deep golden brown and a toothpick inserted into the center comes out clean, about 1 hour.
   
   
   When measuring flour, spoon it into a dry measuring cup and remove any excess. Scooping flour directly from the bag with a measuring cup will compact it, resulting in dry baked goods.
8. Let cool in the pan for 20 minutes, then invert the cake onto a plate, then invert it onto a wire rack to cool completely.