Thats Some Kind of Tuna Casserole

Name: That's Some Kind of Tuna Casserole
Ingredients: 1 1/2 tablespoon olive oil; 1 medium vidalia onion; 1 tablespoon kosher salt; 2 tablespoons lemon juice; 8-10 ounces large shell pasta; 1/4 teaspoon chipotle chili powder; 3 tablespoons sweet pimento; 1/4 cup milk; 10 3/4 ounces cream of mushroom soup; 3 tablespoons capers; 2 tablespoons apple cider vinegar; 1/2 cup breadcrumbs; 12 ounces tuna in water; 2-3 tablespoons butter; 4 ounces shredded mexican cheese blend; 2 tablespoons crushed black pepper