Combine the chili powder, ground cumin, paprika, garlic powder, onion powder, dried oregano, kosher salt, ground black pepper, cayenne pepper, and cornstarch in a bowl; whisk until evenly mixed.
Transfer the taco seasoning to a clean, airtight jar and label. Store in a cool, dark place for up to 6 months.
To use: Brown 1 lb ground meat over medium heat. Stir in 2 tablespoons of seasoning and about 0.5 cup water, then simmer, stirring, until saucy and the seasoning clings to the meat, 3–5 minutes.
Use immediately or hold warm; adjust heat by adding a pinch more seasoning if desired.