This recipe is for a dish called the national snack of Peru. It's prepared and sold by street vendors all over the country. Traditionally it is made with beef heart, but I've substituted sirloin for a more tender kebab. Achiote paste is made from the red seeds of the annatto tree and is used as a seasoning and to impart a yellow coloring. Available in Latin markets, mail order, or in speciality sections of grocery stores, the paste is much easier to use than the seeds.
Heat the oil in saucepan until hot and simmer the cumin seeds in the oil for 5 minutes. Strain the oil and discard the seeds.
Place all the ingredients, except for the beef and onion, in a blender and or food processor and puree until smooth. Put the beef and onions in a nonreactive bowl or plastic bag, cover with the mixture and marinate for 2 to 4 hours, or overnight in the refrigerator.
Thread the beef and onion wedges on a skewer and grill over a medium fire until medium rare about 10 to 12 minutes, basting frequently with the marinade. Cut one cube open as a sample to check for doneness.