Melt butter in a large Dutch oven over medium-high heat. Add onion and next 4 ingredients; sauté 5 minutes or until tender. Add flour, salt, and red pepper; cook, stirring constantly, until caramel colored (about 10 minutes). Add next 3 ingredients; cook, stirring constantly, 5 minutes or until thick and bubbly. Stir in crawfish; cook 5 minutes or until thoroughly heated. Serve with rice. Garnish, if desired.
*2 pounds frozen cooked crawfish tails, thawed and drained, may be substituted for fresh crawfish.