Sweet Potatoes Stuffed with Black Beans and Spinach

Pierce the potatoes all over with a fork, place on a microwave-safe plate and microwave on high, turning over halfway through, until just tender, 16 to 18 minutes. Ten minutes before the potatoes are finished, heat the oil and garlic in a large skillet over medium heat. Add the beans, cumin, cayenne, and 2 tablespoons water, increase the heat to medium-high and cook, tossing, until the beans are heated through, about 2 minutes. Add the spinach, season with 1/4 teaspoon salt and cook, tossing until beginning to wilt, 1 to 2 minutes; remove from heat. Split the potatoes and season with 1/4 teaspoon each salt and pepper. Squeeze a lime wedge over each potato, then top with the bean mixture. Serve with a dollop of yogurt, sliced scallions, and extra lime wedges, if desired.