In a large food processor, combine beans, artichoke hearts, garlic, lemon peel, lemon juice, salt, and cayenne pepper. Cover and process until nearly smooth, stopping to scrape down sides as necessary.
Transfer bean mixture to a serving bowl; stir in the thinly sliced green onion. Serve immediately or cover and chill for up to 2 days. If chilled, let stand at room temperature for 30 minutes before serving.
To serve, garnish with sliced green onion tops. Serve with assorted vegetable dippers and/or crackers.