Heat a large skillet over medium heat. Add the canola oil and onion, and cook until the onion becomes translucent.
1 tablespoon cooking oil, ½ white onion
Add the garlic, and cook until it becomes fragrant, about 1 minute. Then add the shrimp, and cook until they start to curl and turn pink. Remove the shrimp from the pan, and set aside.
2 garlic cloves, 24 ounces large shrimp
While the shrimp cooks, bring a large pot of water to a boil, add the pasilla, chile arbol, and guajillo peppers, and boil for 10 minutes.
3 dried pasilla peppers, 2 dried chile de arbol, 1 guajillo peppers
Drain the peppers, and add them to a large blender along with the tomatoes, apple cider vinegar, cumin, coriander, oregano and salt. Blend until smooth.
6 roma tomatoes, 2 tablespoons apple cider vinegar, 1 teaspoon cumin, 1 teaspoon dried coriander, 1 teaspoon dried oregano, ½ teaspoon salt
Strain the sauce through a fine mesh sieve into the pan that was used to cook the shrimp. Cook for 5 minutes or until the sauce begins to come to a low simmer.
Stir in the shrimp and cook for another 3-4 minutes or until the sauce reaches the desired thickness. Serve with freshly chopped cilantro for garnish and Mexican rice or pasta if desired.
See post for storage options.