Preheat your grill to 350ºF and grease the grates.
In a large bowl, toss sweet potatoes with oil, salt, and pepper.
Place on grill and let cook for 15 minutes on each side until tender.
While grilling, add all dressing ingredients into your blender and blend until smooth. Set aside.
When the sweet potatoes have 10 minutes left on the grill, add sliced onion to the grill and let cook for 10 minutes or until soft and fragrant.
Once done grilling, gently toss sweet potatoes and grilled onion with dressing (amount as desired).
Assemble: Place sweet potatoes and red onion on a plate. Top with more dressing if desired, feta (optional), black beans (optional), bacon (optional), parsley, cilantro, and scallions. Serve warm or cold with lime wedges.