Preheat the oven to 325°F. Spray a 9X5 inch loaf pan with a baking nonstick spray. Line the bottoms and 2 sides of the pan with parchment paper and spray again.
In a mixing bowl, sift the flour. Add the baking powder and salt. Set aside. Zest the lemon and prepare the lemon juce. Set aside. Quarter the blackberries and place in a small bowl. Add the 1 Tablespoon of flour and stir until the blackberries are coated in flour.
2 ⅓ cup All-purpose flour, 2 teaspoon Baking powder, ½ teaspoon Salt, One large lemon zested, ¼ cup Lemon juice, 6 oz Fresh blackberries, 1 tablespoon All-purpose flour
Using a mixer, beat the butter and sugar on high speed for 3 minutes. Scrape the bowl. Add the lemon zest, lemon juice, vanilla, and sour cream. Mix on medium until combined.
1 cup Unsalted butter, 1 cup White granulated sugar, ⅓ cup Sour cream, 1 teaspoon Pure vanilla extract
Add the eggs in one at a time and mix on medium speed. Add in the dry ingredients and mix on low speed.
3 Large eggs
Take off the mixer, and use a rubber spatula to fold the blackberries into the batter.
Fill the pan ¾ths full. There will be unused batter.
Bake for 50-60 minutes. Bake until a toothpick inserted comes out clean.
Let the bread sit in the hot pan for 10 minutes. Then, transfer to a cooling rack and cool completely.