Place a 12-inch skillet over medium heat. Add sausage; cook 4 to 5 minutes or until lightly browned on all sides. Add onion, bell pepper, and garlic; cook over medium-high heat 5 to 7 minutes or until vegetables are tender. Add crawfish tails and Cajun seasoning. Remove from heat.
Cut bread in half lengthwise. Cut each half crosswise into 3 equal pieces. Place bread, cut side up, on a baking sheet. Spread sauce over bread halves; top evenly with crawfish mixture. Sprinkle with cheese.
Bake at 425° for 13 minutes or until cheese melts. Serve immediately.