Tuscan Tuna Sandwich

Name: Tuscan Tuna Sandwich
Prep time: 20 min
Total time: 20 min
Cuisine: American
Ingredients: 1/2 cup tahini (alternately you can use mayo (but I don't love mayo)); 1/4 cup plain greek yogurt; zest + juice of 2 lemons; 2 tablespoons olive oil; 1/2 cup fresh basil; salt + pepper (to taste); pinch of crushed red pepper flakes; 2 (5 ounce) cans oil packed tuna, oil drained; 1/4 cup kalamata olives; 2 tablespoons sun-dried tomatoes (chopped); 1 loaf ciabatta bread (halved lengthwise); 1 avocado (sliced); 2 Persian cucumbers (sliced); 4 hard boiled eggs (sliced or quartered); 1 cup shredded purple cabbage; 2 cups fresh arugula; 4-6 ounces feta cheese (crumbled)