Place garbanzo beans into a large container and cover with at least 2 inches of cool water; let stand at least 12 hours.
Drain garbanzo beans and transfer to a large pot; add enough water to cover beans by at least 2 inches. Bring water to a rolling boil, reduce heat to medium-low, and simmer until beans are very tender, about 2 1/2 hours. Remove pot from heat and cool water and beans to room temperature; drain and transfer beans to a glass container and cover. Refrigerate beans, 8 hours to overnight.
Combine beans, tahini, olive oil, salt, citric acid powder, garlic powder, onion powder, allspice, cumin, coriander, and cayenne pepper in a food processor; add 1/2 cup water. Process mixture for 1 minute. Check consistency of hummus and add 1/4 cup water if hummus is too thick; process again until smooth.
Continue processing hummus in the food processor until hummus is warm, about 15 minutes more.
You can vary the spices to suit your tastes. The ones listed above create a good base flavor. You can also add fresh spices or vegetables.
I'll often add a half onion or a few cloves of garlic instead of the onion or garlic powder. If you use fresh onion or garlic, make sure to put them in at the beginning and consider running the food processor a bit longer - up to 20 minutes. This will mellow the flavor a bit.
You can also add roasted peppers. I find it's best to add these toward the end when there's not more than a minute left to go on the food processor step.
You can make the hummus right away instead of chilling overnight. The hummus will taste fine, but I find that both the consistency and taste seem to be improved by waiting.
Remember it will thicken up a bit in the refrigerator, so it's okay for it to be a little bit soft after adding the water to the food processor. I find that 3/4 cup water is usually the right amount, but the exact amount varies a bit from batch to batch.
If you like very very creamy and smooth hummus, you can transfer from the food processor into a blender (ideally, a commercial grade like a VitaMix®) and blend for a few minutes. I usually don't bother with this, but sometimes I do, and some people seem to prefer it.
Per Serving: 136 calories;8.7 g fat;
11.3 g carbohydrates;
4.1 g protein;
0 mg cholesterol;
177 mg sodium.