1. Combine flour and Cajun seasoning in a shallow dish.
2. Heat oil in a large nonstick skillet over medium-high heat to 360°. Dip tomato slices in buttermilk, and dredge in flour mixture. Fry tomatoes, in batches, 2 minutes on each side or until golden. Drain on a wire rack over paper towels; set aside.
3. Heat bacon according to package directions; keep warm.
4. Split rolls, and arrange, split sides up, on a baking sheet. Broil 5 inches from heat 2 minutes or until lightly toasted; remove from oven.
5. Spread cut sides of rolls with mayonnaise; place fried green tomatoes on bottom roll halves. Top evenly with bacon, avocado, and lettuce; sprinkle with hot sauce, if desired. Top with remaining roll halves, and serve immediately.