Half fill a cooking pot with water and add the black-eyed peas. Bring to a boil and let them boil for 1 minute. Then strain in a strainer.
Add the black-eyed peas back in the pot along with 1,5 liter of water, the onion, celery, carrot, and garlic.
Bring to a boil, then reduce heat to medium and simmer partly covered for 45 minutes to 1 hour. Or until peas are tender enough but not overcooked and mushy.
Season with salt and pepper, add the tomato sauce, chili pepper (whole), dried oregano, and olive oil. Add a splash of water if needed. Cook for another 30 minutes stirring every now and then until the soup thickens. Remove from heat and set aside.
In a frying pan or skillet, add a splash of olive oil and heat over high heat. Add the sausage and cook for 4-5 minutes until nicely browned and seared all over.
Serve the soup topped with the fried sausage. Or you may stir the sausage into the soup depending on your liking.