Carne asada tacos with chipotle marinade, grilled knob onions and nopales

Roast a head of garlic in its papery skin in a pan over medium heat for 10 to 15 minutes until splotchy dark; cool and peel.

Put the garlic in a blender jar with the apple cider vinegar, Worcestershire sauce, olive oil, chipotles, a few tablespoons of their canning liquid, agave syrup and the salt.

Grind the cumin seed, black pepper and Mexican oregano to a powder in a molcajete and add to the blender.

Blend to an absolutely smooth puree.

Rub the marinade over every piece of meat in a marinating dish, stack, cover and marinate no more than about 15 minutes; an acidic marinade left longer makes the meat mealy.

Spray the knob onions and cleaned nopales generously with oil and sprinkle with salt.

Grill the onions with the bulb ends toward the hottest part of the fire and the greens on the cool side, salting again on the grill; add the nopales, cover and cook over medium-high heat, turning the nopales occasionally, until the onions are tender and the nopales are olive green and limp.

If the nopales are not cleaned, cut the nodes off all the way around the circumference to remove the spines.

Cool the vegetables completely on a rack over a sheet pan before cutting, so the nopales are not sticky; chop and sprinkle the nopales with a little salt.

Spray the meat with oil and lay it oil side down on the hottest part of the grill; char a few seconds on each side and flip. The sweetener makes it brown quickly and stick, so clean the grates between batches.

Rest the grilled meat on a rack over a half sheet pan; grill in rounds.

Cut the meat into small pieces and warm it briefly in the oven just before serving.

Build the taco: a little guacamole in the base, a touch of black beans, the meat, onions, salsa verde and chopped nopales on top.