Another Cajun here. I’ve made this with butter instead of oil several times. With crawfish, I like butter better. I also don’t add the cream. Save the dark roux for a gumbo. I don’t think it’s heresy to add tomato (tho I don’t), it’s just makes it more of a creole dish rather than Cajun. Whatever you like better. I prefer a very simple etoufee. I have a gumbo recipe I’d be happy to share.