- Heat oil in a large skillet over medium heat. Add onion (halved and thinly sliced) and chard stems and cook, stirring often, until softened, 3 to 5 minutes.
- Add tomato (chopped), broth (or water), chipotle to taste and salt; bring to a simmer. Add chard leaves and cook, covered, stirring once, until just tender, about 2 minutes.
- Scatter cheese evenly over the chard and cook, uncovered, until the cheese is melted, 1 to 2 minutes more. Serve immediately.