Prep. Preheat oven to 350°F. Line a loaf pan with parchment paper.
Beat butter and sugar, then add eggs. Beat butter and sugar on medium-high for 3-5 minutes until light and fluffy. Add eggs one at a time, mixing well after each.
Mix dry ingredients. In a separate bowl, whisk flour, baking powder, and salt. Add to butter mixture alternately with sour cream, beginning and ending with flour mixture.
Combine wet and dry. Add dry ingredients to the butter mixture alternately with sour cream, beginning and ending with flour mixture.
Add fruits and vanilla. Stir in lemon zest, lemon juice, and vanilla. Gently fold in blackberries by hand.
Fill pan and bake. Pour into prepared pan and bake 60 minutes or until toothpick comes out clean.
Cool. Cool in pan 15 minutes, then remove and cool completely on wire rack.
Make glaze and pour on top. Whisk together powdered sugar, lemon juice, and cream for glaze. If you have any lemon zest leftover, throw it in there. Pour over cooled cake. Pour in the center and let it drip. down the sides. Let it set for an hour or so, then slice.