Cajun Sofrito Ketchup

In a skillet, heat the oil until shimmering. Add the green pepper and onion and cook over moderately high heat, stirring, until lightly browned, 3 minutes. Add the tomatoes and Cajun spice and cook over moderate heat, stirring, until the tomatoes have broken down, 8 minutes. Off the heat, stir in the ketchup. Let cool, then transfer to a jar.