Actually, I will be making a crawfish stew tonight.
First, you make a roux. In this case, I make a tomato paste roux. Melt two sticks of butter (don't <span style="font-weight: bold">even</span> think about using margarine here) and empty a whole, small can of tomato paste (Not sauce) into the simmering pan. Cook low for about 45 minutes until the tomato paste breaks down into small BB-shaped pieces and is dark burgundy in color. Add some chopped onions (one large) until they blanch. Add about 4 tbs of flour and cook some more. The tomato paste will break down into a sweet, not acidic tomato product and will impart a nice pink, slightly sweet base for your stew (as opposed to an ettoufee, which has no tomato). Add water until this thickens under low heat to a rather thick gravy. Cook a bit longer, add your favorite Cajun seasoning, or salt and black or cayenne pepper. Dump 4 lbs of Louisiana peeled crawfish (may use Chinese crawfish, if you must! Or works well with peeled shrimp, too!) Cover and cook for another 30 minutes till the seafood is done. Serve over rice....