Chilies de Arbol – 15,000-30,000 Scoville units. Similar in flavor to cayenne but a bit brighter. Medium to fiery heat. This is the ground chile you often see sprinkled on fruit in Mexico. A favorite chef friend of mine grinds these in-house, for the chile flakes in his Italian restaurant. I now do too as they beat purchased chile flakes by a mile. Lightly toast in a 375°F oven then discard stems and save the seeds in a separate bowl. Grind the flesh into rough flakes and mix back with the reserved seeds. Voila.

From https://stresscake.wordpress.com/2016/01/26/make-your-own-chili-powder/