Melt 1 cup butter in a heavy stockpot on low heat. Whisk in flour gradually to combine. For best flavor, the heat should remain low and the flour and butter will slowly brown to a butterscotch color. This will take about an hour or more. Stir occasionally. The butter/flour mixture is called a roux, which provides flavor and thickening to the gumbo. Don’t rush this step!
While the roux is cooking, melt 1/4 cup butter in a large skillet; add onions, pepper and celery. Cook and stir occasionally until vegetables are tender, about 5 minutes. Add to the finished roux. Stir in okra, garlic powder, chicken broth, Cajun seasoning, tomatoes and sausage. Simmer for 20 to 30 minutes. Add seafood and simmer 10 to 15 minutes until shrimp is done.
Remove from heat. Stir in gumbo file. Hot sauce may be added at this time, or simply served at the table.
To serve, ladle gumbo over bowls of hot rice.
Roux maybe prepared ahead and refrigerated. Sauté onions, peppers and celery as directed and then add roux, stirring until it has melted. Proceed with recipe as directed.