Barbecue Pork Tenderloin with Collards and Lentils

Name: Barbecue Pork Tenderloin with Collards and Lentils
Ingredients: 1 pork tenderloin (about 1 1/4 pounds); Kosher salt and freshly ground pepper; 3 tablespoons extra-virgin olive oil; 1/4 cup barbecue sauce; 1 small onion, chopped; 1 large stalk celery, chopped; 3 to 4 sprigs thyme; 1 15-ounce can lentils, drained and rinsed; 2 cups frozen chopped collard greens, thawed; 1/4 cup jarred sliced hot cherry peppers, roughly chopped, plus 2 to 3 tablespoons brine; 2 cloves garlic, finely chopped; Cornbread, for serving