Goat meat tacos are a popular dish in the Mexican state of Jalisco, where they are called Birria. The dish is often served at celebratory events like weddings and baptisms, and are often featured on holiday tables at Christmas and Easter. Preparation techniques vary from home to home, but the dish is frequently served with inion, cilantro, lime and corn tortillas.
Combine cumin, sherry vinegar, olive oil, garlic, red pepper flakes, cinnamon, brown sugar, chili powder, and tomatoes, whisk to combine.
Place the goat shanks in a large bowl, add 2/3 of the marinade, coating on all sides.
Preheat oven to 350° F. Season the shanks with salt and pepper, transfer to the oven and braise until very tender, approximately 2 hours. Flip the goat shanks at one hour.
Remove from the oven and let cool slightly. Skim off any excess fat and spoon any reduced marinade from the pan into a small mixing bowl. Mix with the reserved (uncooked) marinade.
Remove the shanks and pull the meat off the bone, discarding the bones and fat.
Shred the meat with forks and transfer to a bowl. Pour the warmed braising liquid over the meat and toss to coat.
In a dry pan, brown the tortilla on both sides.
Divide the goat among corn tortillas and top with cilantro and onion.