Combine first nine ingredients and blend together well. Place in zip lock bag, add steaks and marinate six hours.

Peel and pit avocado, cut into chunks. Combine all salad ingredients and mix gently. Season to taste with salt and pepper.

Prepare charcoal grill to medium-high heat (or preheat a heavy grill pan over medium-high heat on stove). Remove flat iron steaks from marinade and place on grill.

Cook approximately four minutes per side and check for doneness using instant read thermometer (135 degrees for medium rare). Place steaks back on grill to cook more or let rest with a foil tent over them.

Slice baguettes lengthwise and place on grill cut side down. Toast for one minute, then flip and place sliced cheddar cheese on cut sides. Allow cheese to melt.

Slice Brandt Beef flat iron steaks across the grain, place on baguette and top with avocado salad. Cut each baguette into three portions and serve.