Pre-heat oven to 450 degrees, IN a 9x13 in. baking dish whisk
flour, 1/4 cup sugar, baking powder, baking soda and salt in a medium bowl until blended. Cut in butter until coarse crumbs form. Refrigerate flour mixture and buttermilk seperately until ready to top cobbler.
Mix sugar, zest
and lemon juice mixture in a large deep skillet over high heat. Stir in 1/2 pint of the blueberries and cook appx. 10 mins. Stir in rest of blueberries, the blackberries and the vanilla. Spread in baking dish.
Stir flour mixture and buttermilk with a fork until a biscuit-like dough forms. Drop 8 1/4 cup fulls evenly spaced over hot filling. Sprinkle with remaining sugar. Bake
15 to 20 mins. Serve warm or at room temp.