1 (1-pound) pork tenderloin, trimmed and cut crosswise into 1-inch-thick medallions
1/2 teaspoon kosher salt
1/2 teaspoon freshly ground black pepper
1 tablespoon extra-virgin olive oil
1 1/2 teaspoons chopped fresh rosemary, divided
4 canned anchovy fillets, drained and mashed
3 garlic cloves, thinly sliced
1 red bell pepper, cut into 1 1/2-inch strips
1 yellow bell pepper, cut into 1 1/2-inch strips
2 teaspoons balsamic vinegar