Place the sweet potatoes into a 4-quart saucepan and add water to cover. Heat over high heat to a boil. Reduce the heat to medium. Cook for 12 minutes or until the sweet potatoes are tender. Drain the potatoes in a colander and return to the saucepan. Cover and keep warm.
While the potatoes are cooking, heat the oven to 425°F. Combine the cumin, thyme, garlic powder and black pepper in a small bowl. Rub the pork with the cumin mixture. Season with salt, if desired.
Heat the oil in a 12-inch cast iron skillet over medium-high heat. Add the pork and cook until well browned on all sides (to prevent sticking, make sure the skillet and oil are hot before adding the pork). Place the skillet into the oven and bake for 12 minutes or until done. Let the pork stand for 5 minutes before slicing.
Add the soup to the sweet potatoes in the saucepan and mash until smooth. Season with salt and pepper. Serve the sweet potatoes in bowls, topped with the sliced pork. Sprinkle with the red onion, if desired, and the cilantro.
This nutritional information refers to each serving of the entire recipe and not just the products used as ingredients.