Kitchen Sink Quesadillas

Name: Kitchen-Sink Quesadillas
Ingredients: 1 15.5-ounce can black beans, drained; 1 11-ounce can corn kernels, drained; 3/4 cup salsa, drained; 1 8-count package large flour tortillas; 1 1/2 cups (6 ounces) shredded Cheddar or Monterey Jack; 1 small red onion, thinly sliced; 1/3 cup fresh cilantro leaves; 1/2 teaspoon kosher salt; 1/4 teaspoon black pepper; juice of 1 to 2 limes; 2 tablespoons extra-virgin olive oil; 1 head romaine lettuce, sliced 1 inch thick