Achiote paste is a seasoning made with annatto seeds, vinegar, garlic, salt, and spices. It gives tacos al pastor a distinctive red color and earthy flavor. If you can’t find it, you can make your own by grinding 2 tablespoons of annatto seeds with 1 teaspoon of cumin, 1/2 teaspoon of oregano, 1/4 teaspoon of allspice, 1/4 teaspoon of cloves, 4 cloves of garlic, 1/4 cup of vinegar, and salt to taste. You can also substitute it with paprika, turmeric, or tomato paste, but the flavor and color will be different.