Stunningly Good Chickpea Tuna Melt

Name: Stunningly Good Chickpea Tuna Melt
Prep time: 5 min
Cook time: 10 min
Total time: 15 min
Cuisine: American
Ingredients: 1 15-oz can chickpeas (drained, 425 g); ¼ cup finely diced red onion (about ¼ of a medium onion); ¼ cup finely chopped celery (about ½ a stalk); 1 tsp capers (finely chopped); ¼ cup mayonnaise; 1 tsp Dijon mustard; 2 tsp white vinegar; Salt and pepper (to taste); 4 slices sourdough bread; 1 Tbsp mayonnaise (15 g); 2 slices tomato; 2 slices sharp cheddar cheese (can sub provolone)