Heat the oil in a large pot over low-medium heat. Add the onions and cabbage. Stir well to coat with the oil. Cover and cook for 10 minutes, stirring occasionally, until the onions and cabbage are wilted. Add the tomatoes and water. Stir well to combine. Raise the heat to high. Cover and bring to a boil, then lower the heat to low-medium and continue cooking, covered, for about 30 minutes, stirring occasionally. Stir in the brown sugar, lemon juice, raisins, salt, and pepper to taste. Mix well to combine. Taste for seasonings.