In a medium skillet over medium heat, roast garlic, turning frequently, until softened, about 15 minutes. Remove from heat, cool and slip off skins. Set aside.
Bring about 8 cups of water to a boil, drop in beans. Bring back to a boil and cook for 5 minutes. Reserve 3/4 cup of cooking water before draining. Drain the beans and cool.
Transfer garlic to a blender and chop coarsely. Add beans, salt, cayenne pepper and cumin. Process in blender, adding reserved water a little at a time until smooth. (You may not need to add all of the water.) Add olive oil, lime juice and cilantro. Pulse to combine.