Start by caramelizing the onions. Heat a large skillet or frying pan over medium heat. When it's hot, add the onions. Stir the onions frequently.
Once they soften and start to turn golden (5-10 minutes), reduce the heat to medium-low. Add 2 tablespoons of water, stir the bottom of the pan, and continue cooking the onions, stirring them often until all the water is cooked off.
Repeat the process of adding water, stirring, and cooking the water off a few more times until the onions are a deep brown color. I usually do this 3-4 times. The whole process will take about 40 minutes.
When the onions are dark (not burned) and the liquid is absorbed, add the balsamic vinegar and do a final pan deglazing (clearing the bottom of any stuck-on onions). Cook until all the liquid is absorbed. Remove the onions from the heat and set aside while you make the hummus.
Add the chickpeas, ¼ cup of aquafaba, garlic, tahini, lemon juice, onion powder, smoked paprika, cumin, black pepper, and salt to a food processor or blender. Blend until the hummus is smooth, adding more aquafaba as needed. Note: Save a few of the whole chickpeas for a garnish if desired.
Add ¾ of the balsamic onions to the hummus and pulse a few times to blend them in (longer if you want the hummus super-smooth).
Transfer the hummus to a bowl. Taste and add more salt or lemon juice if desired. Garnish with the remaining balsamic onions and chickpeas (if you saved a few).