Measure out all the spices and cornstarch as listed.
Combine chili powder, salt, paprika, sugar, onion powder, garlic powder, cumin, cayenne pepper, and cornstarch in a bowl.
Mix thoroughly until all ingredients are evenly blended.
Store the seasoning mix in an airtight container or jar.
Use approximately 1 tablespoon of seasoning per pound of chicken for fajitas.
Toss the chicken with the seasoning before cooking for best flavor.
Adjust spice levels by adding more or less cayenne pepper as desired.
Keep stored in a cool, dry place for up to 3 months.