1 15-oz can cannellini beans, rinsed and drained
1 15-oz can kidney beans, rinsed and drained
1 15-oz can garbanzo beans, rinsed and drained
1/2 red onion, chopped fine, soaked in water to take the edge off the onion
2 celery stalks, chopped fine
1 cup fresh, finely chopped flat-leaf parsley
1 Tbsp fresh finely chopped rosemary

1/3 cup apple cider vinegar
1/4 cup granulated sugar (more or less to taste)
1/4 cup olive oil
1 1/2 teaspoons salt
1/4 teaspoon black pepper