In a large serving bowl, combine the beans, dill, and olive oil. Season to taste and marinate for 10 minutes.
Blend together all of the mustard vinaigrette ingredients with a whisk or blender and season to taste.
Add the celery, onion, eggs, fennel, greens, capers, roasted tomatoes, and tuna to the bowl with the marinated beans. Drizzle with dressing and toss to combine.