How to Make It
In a large glass or stainless-steel bowl, whisk together the lemon juice, mustard, salt, and pepper. Add the oil slowly, whisking.
In a medium glass or stainless-steel bowl, combine the tuna and chickpeas. Gently stir in 1/4 cup of the dressing.
Using a stainless-steel knife, peel the oranges down to the flesh, removing all of the white pith. Cut the sections away from the membranes and set aside. Squeeze 2 tablespoons of the juice from the membranes into the remaining dressing.
Add the tuna and chickpeas, orange sections, lettuce, fennel, onion, jalapeño, and cilantro to the dressing and toss gently.