Brown the beef and onion in a skillet over medium-high heat for 9 minutes, breaking the meat into fine crumbles, until it reaches 160°F.
Drain the fat and stir in the garlic, ancho powder and cumin for 30 seconds.
Transfer the beef to a 6-quart crockpot and add the tomatoes, hominy, black beans, broth and salt.
Cover and cook on low for 6 hours until the hominy is tender and the sauce is a deep red.
Whisk the masa harina with the warm water, stir it into the chili, and cook uncovered on high for 30 minutes until the broth lightly coats a spoon.