How to Make It
Preheat grill to medium. Insert a metal skewer through center of onion slice so it will lay flat. Brush onion, tomatillos and jalapeños with oil; sprinkle with salt and pepper. Grill onion for 6 minutes, turning once. Grill tomatillos, turning often, until just beginning to char, 4 to 6 minutes. Grill jalapeños, turning frequently, until blackened, 8 to 10 minutes. Place jalapeños in a bowl, cover with plastic wrap and let steam for 10 minutes. Allow other vegetables to cool.
Roughly chop onion. Core and chop tomatillos. With your fingers, peel charred skin off jalapeños; remove and discard seeds; chop flesh.
Pulse avocados, garlic and grilled vegetables in a food processor until chunky. Add lime juice and cilantro; season with salt and pepper. Pulse until just combined. Transfer to serving bowl. Serve with chips and crudités, if desired.