Beans are the most concentrated food source of natural fiber, making this a healthy dip to serve with raw or steamed vegetables. It is especially satisfying with artichokes, which are often paired with high-fat butter or mayonnaise.
Preheat oven to 350 degrees. Place a medium saucepan coated with olive-oil cooking spray over medium heat. Add chopped onion and garlic, and saute until translucent. Add 1 teaspoon rosemary, cannellini beans, and salt and pepper, and saute until very hot.
Transfer bean mixture to the bowl of a food processor, add white-wine vinegar, 1 tablespoon olive oil, and 3 tablespoons reserved bean liquid, and then puree until smooth.
Combine bread crumbs, Parmesan cheese, remaining teaspoon rosemary, and remaining teaspoon olive oil in a small bowl, and stir until well combined.
Place bean puree in an ovenproof bowl; top with the bread-crumb mixture. Transfer to oven; bake until golden brown, about 20 minutes. Serve hot with toast and assorted vegetables.