Preheat oven 325 degrees F.

Coat the inside of two 9 x 5 loaf pans with butter on the bottom and up the sides.

In the bowl of a stand mixer fitted with a dough hook, cream the butter, sour cream and sugar.

Add the eggs in four parts, mixing on low and scraping the bowl in between additions.

Add the salt and vanilla.

Add the flour, one half cup at a time and continue mixing on low and scraping the sides of the bowl down in between additions.

Once everything is incorporated well, remove the dough hook and fold in the berries.

Divide the mixture between the two loaf pans.

Tap the pans to remove any air pockets.

Bake in the oven for one hour or until a toothpick inserted into the center comes out clean.

Remove from oven and allow the cakes to cool in the pans for 30 minutes.

Remove the cakes from the pans and set on a cooling rack until completely cooled before slicing and serving.

In a small saucepan, combine the blueberries, lemon juice, vanilla and salt.

Bring to a boil over med/hi heat.

Turn the heat to med/low and simmer until the berries open.

Combine the corn starch and cold water to make a slurry.

Stir the slurry into the blueberry mixture and remove from heat when thickened.

Serve the sauce over the cooled cake slices.