Preheat your grill to medium heat, around 375-400°F (190-200°C). If you’re using a grill pan, heat it on the stove until hot.
Wash and dry the sweet potatoes. Cut them into wedges: start by slicing in half lengthwise, then cut each half into 4-6 wedges depending on potato size.
In a large bowl, toss the wedges with olive oil until they’re lightly coated.
Mix the chili powder, smoked paprika, cumin, garlic powder, salt, and a pinch of pepper in a small dish. Sprinkle the spice mix over the wedges and toss well to coat all sides.
Grill the wedges in a single layer. If you need to do them in batches, keep the finished wedges warm on a plate covered loosely with foil.
Grill for 3-4 minutes per side, or until the edges are crisp and the centers are tender. You want some caramelization—those little char marks make the flavor pop.
While they’re grilling, whisk together the lime juice and zest. Once the wedges come off the grill, drizzle with the lime and toss to coat. Finish with cilantro if you like.
Taste and adjust: a little more lime juice, a pinch more salt, or a light dusting of chili powder if you want extra kick.