Remove the seeds and veins from the guajillo and ancho chiles.

In a pot with about 4 cups water (1 liter), add the cleaned chiles and boil for 15 minutes.

In a blender, combine the boiled guajillo and ancho chiles, garlic cloves, whole cloves, cumin, oregano, achiote paste, salt, orange juice, vinegar, and 1/4 of the pineapple (cut into pieces). Blend until you have a smooth marinade.

Place the pork slices one by one in a large skillet or dish and pour the marinade over them, making sure they are well coated. Let marinate for 30 minutes.

In a skillet with a little oil, fry the marinated pork until fully cooked. Remove and chop the meat for tacos. Without turning off the skillet, add the onion (cut into thin strips) and the remaining 1/4 pineapple (finely chopped). Cook for 10 minutes.

Return the chopped pork to the skillet with the onion and pineapple. Mix well and cook for another 10 minutes. The meat for tacos al pastor is ready.

Traditional salsa for tacos al pastor: In a blender, combine 6 arbol chiles, 1 garlic clove, 5 Roma tomatoes, 1/4 onion, 1 tablespoon salt, and 1/2 cup water. Blend everything raw until smooth. The salsa is ready.