Mix minced onion, salt, chili powder, cornstarch, cumin, red pepper flakes, cayenne pepper, minced garlic, and oregano in a bowl; set seasoning mix aside.
Heat a large skillet over medium-high heat. Cook and stir ground beef in the hot skillet until browned and crumbly, 7 to 10 minutes. Drain and discard any excess grease.
Pour water and seasoning mix over beef; stir to combine. Bring to a simmer and cook until mixture thickens slightly, about 5 minutes.