Preheat oven to 325F degrees.
Spray 2 - 9" loaf pans with Bakers Joy (I highly recommend this product for all cakes)
In mixer- cream together your sugar & butter. Beat until fluffy.
Add eggs – one at a time & beating in-between each addition
Scrape bowl down. Add lemon juice & vanilla
Add in flour, baking powder, baking soda & salt.
Top with sour cream & then beat to combine – do not over mix.
Gently fold in blueberries by hand with large spatula
Pour into prepared pans.
Top each with jam & then run a knife through a couple times to swirl it throughout.
Bake 60- 75 minutes or until toothpick test is clean.
Cool on wire rack at least 10 minutes before removing from pan & then continue to cool on wire rack until room temperature before cutting.