How to Make It
Place the potatoes and 1 inch of water in a microwave-safe dish, cover, and microwave on high until the potatoes are soft, 10 to 12 minutes. Drain and rinse with cold water to stop the cooking; set aside.
Meanwhile, chop the chard stems and thinly slice the leaves. Heat the oil in a large skillet over medium-high heat. Add the onion and cook, stirring occasionally, until translucent, 4 to 5 minutes. Add the chard stems and cook, stirring occasionally, until crisp-tender, 1 to 2 minutes.
Add the chard leaves and broth and cook until the leaves are tender and the broth is almost evaporated, 4 to 6 minutes. Add the potatoes, ½ teaspoon salt, and ¼ teaspoon pepper and cook until just warmed through, 1 to 2 minutes more.
Stir in the lime juice and sprinkle with the Cotija.