Preheat oven to 350° F. Spray a 9 x 5-inch loaf pan with baking spray, set aside.
Wash and rinse the blackberries, and carefully dry with a paper towel to remove excess moisture.
Beat the butter and sugar together in a large bowl with a hand mixer until light and fluffy.
Mix in the eggs one at a time. Add the yogurt, lemon juice, lemon zest, and vanilla. Mix well, scraping down the sides of the bowl as you go.
Sift the flour, baking powder, and baking soda, into the wet ingredients. Stir the ingredients together with a rubber spoon only until combined, do not over mix!
In a small bowl, mix blackberries with 1 tablespoon of flour. Gently fold about two-thirds of the blackberries into the blackberries (minus the additional flour) into the batter.
Pour batter into prepared pan, add the remaining blackberries on top, and use a spoon or knife to smooth out the batter.
Bake for 50 – 60 minutes, or until golden brown and a toothpick inserted into the center of the bread comes out clean or with a few moist crumbs (not wet batter).
Place loaf pan on a wire rack to cool for 20 minutes. Remove from pan and allow to cool completely on the wire rack.
Notes
Do not "tap" down your flour in the measuring cup, or you will end up with a dry batter. Fluff, scoop and flatten off with a knife.
Coating the blackberries in a bit of flour before adding them to the batter helps to prevent excessive bleeding.
Frozen blackberries can also be used in this recipe.
Store the cooled bread in an airtight container or wrap it tightly in plastic wrap. It can be kept at room temperature for a day or two, but for longer storage refrigerate or freeze.