Cowpoke Sandwich 1 large onion, sliced thick Cilantro and Mexican oregano, dried, crumbled Salt and pepper Bread slices, buttered Vinegar and water, in equal amounts Cayenne pepper, to taste Put onion slices in a bowl. Coat with spices, then cover with water and vinegar mixture. Refrigerate for 8 to 10 hours. Drain onion slices, season with salt, pepper and cayenne. Place between two slices of buttered bread.