Combine 1/4 cup plain yogurt, the zest of 1/2 lime and a pinch of salt; set aside. Cook 1/2 chopped red onion in 3 tablespoons vegetable oil in a large nonstick skillet over medium heat, stirring, until tender, about 5 minutes. Stir in 1 teaspoon curry powder, 30 seconds. Add half a 28-ounce bag frozen hash-brown dices and cook, stirring occasionally, until golden, about 12 minutes. Stir in 1 cup thawed frozen peas. Cook until warm, 1 to 2 minutes. Toss with 1/2 cup chopped cilantro. Drizzle with the yogurt.