Place the wood chips in a small cast-iron skillet and light them on fire. Place the cast-iron pan into a roasting pan and place the onion beside the skillet. Cover the roasting pan with aluminum foil and smoke the onion for 20 minutes.
Transfer the onion to a food processor and puree until smooth. Add 1 teaspoon of the salt, stir to combine, and set the puree aside.
Place the avocado oil in a large cast-iron skillet and warm it over high heat. Add the eggplant, season it with the remaining salt, and sear it for 1 minute. Turn the eggplant over, add the bell pepper, and cook for another minute.
Add the balsamic vinegar and toss to coat.
To serve, spoon the onion puree onto the serving plates and top with the vegetables.
