1. Place beef in a large pot with garlic, ginger, spice blend, and chicken stock. Bring to a boil; reduce to a simmer and cook, uncovered, until tender, 3 to 4 hours. Remove meat from pot and transfer to a rimmed baking sheet, reserving the cooking liquid. Let meat dry, 2 to 3 minutes.

2. Heat oil over medium-high in a Dutch oven or braiser. Working in batches, sear beef until browned all over, then return to baking sheet. Set Dutch oven aside to cool slightly. Using two forks, shred beef into 2-inch chunks. Return pot to low heat and add 2 cups reserved cooking liquid, stirring to deglaze. Add beef and tomato sauce, then bring to a simmer, cover, and cook for 15 minutes, stirring in additional reserved cooking liquid if the sauce becomes dry.

3. To serve, transfer half of the rice to a large shallow serving dish. Top with half of the meat mixture. Cover with remaining rice, then spoon remaining meat mixture on top. Garnish with caramelized onions and cilantro.