On a griddle on medium high-heat, toast corn tortillas until crispy and slightly charred. Set aside. On the same griddle, toast dried chiles for 1 minute on each side, taking care not to burn. Put chiles in a bowl and cover with boiling water. Use a small plate to keep chiles submerged for 30 minutes.
On same hot griddle, slightly char onions and garlic, about 4 minutes. Peel garlic and place it with onions in blender. Put whole tomatoes on griddle and turn often to char on several sides, then add to blender. When chiles have finished soaking, drain, and add to blender.
On same hot griddle, toast pumpkin seeds until they begin to puff up. Reserve 1/4 cup of pumpkin seeds for garnish, and add the rest to the blender. On griddle, toast allspice and peppercorns for a few seconds and add to blender wth achiote, salt, and pepper.
Break charred tortillas into quarters and add to blender. Purée until ingredients form a smooth sauce. If necessary, work in batches or add a small amount of water to blender to process smoothly. Sauce should have the consistency of a tomato sauce or just a little bit chunkier.