If you are using dried beans, soak them overnight in water. The following day, drain the beans, rinse, and drain again. Place the beans in a large saucepan with 4 cups of water, and bring to boil. Lower heat to simmer, and cook for 45 minutes to an hour.
Heat the oil in a saucepan over medium heat. Add the onion, and sauté until translucent. Add garlic, tomatoes, cumin, oregano, and sea salt, and cook while stirring for one minute. Add the cooked or canned black beans and water, and bring to a boil.
Turn down the stove to low heat, and allow to simmer for 10 minutes. Remove the saucepan from the stove, partially mash beans to thicken, and set aside.