Working in batches, grind the chile peppers in a spice grinder until finely ground, about 1 minute.
Stir in cumin, paprika, oregano, garlic powder and cayenne.
Notes
Tips:
Toast peppers for a smoky chili powder. Add some smokiness to your chili powder by toasting the dried chili peppers in a dry skillet over medium heat until they are fragrant. Flip them regularly and be careful not to burn them. Cool completely before grinding.
Remove stems and seeds. Break open the peppers and remove the stems and seeds. Seeds are incredibly spicy, so removing them helps you control the heat level better. You can discard or save the seeds as red pepper flakes for future use.
Experiment with different chiles. Use a single variety of chili peppers or combine different types for a complex flavor profile.
Texture preference. Grinding the peppers gives you control over the overall texture of the chili powder, whether you prefer a coarse grind, fine powder, or something in between. Experiment and adjust the duration of grinding to achieve the texture that suits you. You can also throw in the Mexican oregano towards the end and pulse a few times if you prefer them finer.