For the spice mix: Cut the tops off the guajillo chiles, shake out the seeds, put the chiles in a bowl, cover them with boiling water and let them soak for about 30 minutes to rehydrate.
Drain the chiles, then put them in a blender with the oil, ancho chile, cumin, coriander, peppercorns, salt, cinnamon and lime juice and blend until combined.
For the corn: Prepare a grill for medium-high heat.
Cut the corn in half and brush with the spice mix. Cook until charred in spots and grill-marked, turning halfway through, about 6 minutes. Sprinkle with lime juice and cotija cheese.