– Place the tomato, serrano pepper and 1 cup of water in a saucepan, and cook on medium heat until tomatoes and pepper are tender. They will take about 15 minutes to cook.
– While the tomatoes and peppers are cooking. Heat oil in a large skillet over medium heat. Add onion, and cook, stirring, until soft, about 3 minutes.
– Add the chorizo (casings removed) and keep cooking about 8-9 minutes. Stirring from time to time.
– Once the tomatoes and peppers are cooked, place them in your blender with a ¼ cup of the water, and process until you have a smooth sauce. Set aside.
– Stir in the sauce, and let it simmer for a few minutes just to let the flavors to blend. About 5 minutes. Adding more water if the food in the skillet becomes too dry. Season with salt and pepper.