Place the tuna, white beans, parsley, capers, lemon juice, olive oil in a bowl and toss to combine. Taste and add salt and pepper. Let stand for 5 minutes to combine flavors.
Arrange the sliced cucumbers and spinach on 4 plates. Divide the tuna salad among the plates.
Notes
Can sub canned salmon for the tuna. Can sub Kalamata olives for the capers or even roasted red peppers. Can sub baby arugula, kale or any of your favorite lettuces for the baby spinach.