In a blender, puree the diced tomatoes. In a medium saucepan, heat the 2 tablespoons of oil until shimmering. Add the tomato puree and cook over moderately high heat, stirring frequently, until very thick, about 7 minutes. Add the Salsa Negra and 1/3 cup of water and simmer until slightly thickened, about 10 minutes. Season with salt and pepper.