Wash, dry and dice the cherry tomatoes and cucumber. Slice the onions thinly and finely chop the parsley.
In a small bowl, combine the olive oil, lemon juice and zest, minced garlic, mustard, salt, pepper, paprika and sumac. Mix well until all combined.
In a separate bowl, toss the onions with ⅓ of the dressing and set aside for 5-10 minutes. This will soften the sharp flavor of the onions. This is an optional step, you can also toss the onions directly into the salad.
Rinse the can of butter beans well in cold water to remove excess salt. Add to a large mixing bowl along with the chopped tomatoes, cucumber, parsley and marinated onions.
Pour the leftover dressing over the salad and mix until well combined. Serve immediately and enjoy!