Rinse and peel lotus root. To cube lotus root, cut the segment in half lengthwise, slice along the tube, then cut into 1- to 1.5-centimeter (about 0.5-inch) cubes. Prepare and cut the other vegetables.

Bring a small pot of water to a boil. Add lotus root and boil for 1 minute. Drain and set aside.

Heat oil in a wok over medium high heat (high heat on an electric stove) until hot. Add scallion and stir until fragrant. Add lotus root and pepper, and stir until half cooked, about 3 minutes (longer if you use a skillet instead of wok). Add sugar and swirl in vinegar. Immediately stir to mix the seasoning well, about 30 seconds. Sprinkle in salt and stir until mixed well, about 20 seconds. Stop heat and transfer everything to a plate.

Serve warm as side or appetizer.