Drain tomatoes, reserving 1/3 cup liquid; set aside. In a large skillet cook bacon pieces until crisp. Remove with slotted spoon, reserving 1 tablespoon drippings in skillet. Drain bacon on paper towels.
Add onions to drippings in skillet; cook until just tender, about 3 minutes. Stir in beans, tomatoes, and reserved tomato liquid. Cook and stir over medium heat for 2 minutes or until heated through. Stir in 3 cups of the spinach; cover and cook until just wilted, about 30 seconds. Stir in cooked bacon and remaining spinach. Spoon mixture into 4 individual bowls. Drizzle each serving with 1 teaspoon vinaigrette. Makes 4 side-dish servings.