Serves 8 to 10
1 tablespoon cumin seeds
1 tablespoon coriander seeds
1 cup sherry vinegar
1 cup extra-virgin olive oil
10 cloves garlic, smashed
¼ teaspoon red pepper flakes
1 cinnamon stick
2 tablespoons packed light brown sugar
2 teaspoons ancho chile powder
1 16-ounce can crushed tomatoes
1 5-pound bone-in leg of lamb, cross-cut into 5 to 6 pieces (ask your butcher to do this)
Kosher salt and freshly ground pepper
3 tablespoons canola oil
2 12-ounce bottles lager beer (I like Great Lakes Dortmunder Gold)
1 jalapeño pepper, chopped
Corn tortillas, warmed, for serving
Cilantro, for topping
Toast the cumin and coriander seeds in a small skillet over medium heat, swirling the pan, until slightly darkened, about 2 minutes. Transfer to a large bowl. Add the vinegar, olive oil, garlic, red pepper flakes, cinnamon stick, brown sugar, chile powder and tomatoes; whisk to combine. Put the lamb in a large nonreactive container and add the marinade; cover and refrigerate overnight or up to 48 hours.
Preheat the oven to 350˚. Remove the lamb from the marinade and pat dry; reserve the marinade. Season the lamb with salt and pepper. Heat the canola oil in a large Dutch oven over medium-high heat. Working in batches, add the lamb and cook until browned, 3 to 4 minutes per side. Add the reserved marinade, the beer and jalapeño and bring to a simmer. Cover, transfer to the oven and braise until very tender, about 2 hours.
Remove from the oven and let cool slightly. Skim off any excess fat. Remove the lamb and pull the meat off the bone, discarding the bones and fat. Strain the liquid into a smaller pot and keep warm.
Shred the meat with your fingers and transfer to a bowl. Pour the warmed braising liquid over the meat and toss to coat. Divide among corn tortillas and top with cilantro.