Add the oil to a dutch oven or big pot/skillet with high sides over medium heat. Let it warm up for 1-2 minutes, then add the cumin, paprika and cayenne. Reduce heat slightly and stir for about 2 minutes. (this is called blooming the spices!) Add the chopped onion, a sprinkle of salt and a splash of water. Cook over medium heat until the onions are fragrant, about 5 minutes.