Heat a little bit of olive oil in a large skillet over medium heat. Add the onions, salt and pepper and cook until very soft and caramelized, about 20-25 minutes. Add a few tablespoons of water from time to time to help deglaze the pan and soften the onion. Always wait until the water has fully evaporated before adding more.
Arrange one third of the sweet potatoes in a rectangular baking dish. Make sure the potatoes overlap by about half a slice.
Top with half the caramelized onions and spread evenly. Repeat with another layer of sweet potatoes, then add the rest of the caramelized onions, followed a final layer of potatoes. It might be a good idea to keep your prettiest potato slices for the final layer.
Sprinkle chopped pecans evenly over that final layer of potatoes. Set aside.
In a small mixing bowl, or large measuring cup, add all the ingredients of the sauce and mix until well blended.
Very delicately pour over your potato dish, being careful as to not disturb the pecans.
Cover loosely with foil and bake in the oven for 40 minutes, then remove the foil and cook for an additional 15 minutes.
Remove from the oven, drizzle a tablespoon of honey over the pecan crust and return to the oven for an additional 5 minutes.
Remove from oven and allow to rest for 10-15 minutes before serving.