In the bowl of a slow cooker, mix together first 11 ingredients (Balsamic tomatoes through red wine). Set aside.
Heat 2 teaspoons olive oil in a large heavy saucepan over medium-high heat, add sliced onions, and cook until onions are caramelized, about 20 minutes, add in a couple tablespoons of water if the onions appear to be burning or cooking too quickly. Once the onions are nice and caramelized, stir in the flour, and cook, stirring, for 2-3 minutes. Place caramelized onions in the crock pot with the liquid. Wipe out pan.
Heat remaining 2 teaspoons olive oil in the same large heavy saucepan over medium-high heat. Working in batches so as not to crowd the pan, add cubed beef, cooking until well browned on all sides, about 10-20 minutes per batch. Remove beef from pan once it is browned, and place in the crock pot. Deglaze pan with water or red wine between batches.
Turn crock-pot on high, and cook, covered, for about 4-6 hours or until beef is tender. Discard bay leaf.