Heat the oil in a large skillet over medium heat. Once hot, add the peeled onions and sautée for 5-7 minutes, or until they start to brown.
Add the maple syrup and balsamic vinegar and cook for another 2-3 minutes, stirring regularly to prevent the onions from burning. Season with salt and pepper, and add the bay leaves.
Pour in the water and cover with a lid. Let cook covered for 40-45 minutes, or until onions are soft. You can test doneness by using a toothpick or knife, the onions should be very soft.
Remove from heat and transfer to a serving plate. You can eat the onions warm as a side with mashed potatoes, roasts, etc, or transfer to a jar, cover with oil and store in the refrigerator for several weeks.
Sweet and sour onions are delicious as an appetizer, as part of an antipasto platter, or used in salads, hummus, sandwiches, etc.