Step 1Combine chickpeas, onion, garlic, lemon zest, oil, and a couple big pinches of salt in a large pot. Add 2 quarts water and stir to combine. Bring to a boil, then reduce heat to medium-low and simmer, stirring occasionally and replacing any water that evaporates, until chickpeas are tender, about 2 hours. Taste and season generously with salt and pepper. Let cool.Step 2Do Ahead: Chickpeas can be made 6 days ahead. Transfer to an airtight container and chill.