In a medium - large bowl, mix the sweet potato slices with 2 tablespoons of extra virgin olive oil from the 1/3 cup.
On a hot grill or griddle, grill both sides of the sweet potatoes until cooked through.
While waiting for them to cook, prepare the cilantro-lime dressing.
In a small bowl, mix the remaining extra virgin olive oil, cilantro, lime zest, juice, salt, sugar, and pepper. Adjust the quantities according to your liking.
As soon as the sweet potatoes are cooked, put them in a medium - large bowl then pour the dressing while they are still hot. Mix well until all the potatoes are coated.