Leon's Great Open-Faced Steak Sandwich

Directions

Combine the red onion with the olive oil and the chopped rosemary. Let marinate for 1 hour, or as long as 12 hours.
Brush the bread with olive oil, and toast lightly over hot coals or under a broiler. Keep warm.
Grill or broil the minute steak just until rare. Remove from grill or broiler, to a warm plate and let rest for five minutes.
Prepare the sandwich. Spread mayonnaise and Dijon mustard to taste on the bread. Spoon any accumulated juices from the plate over the bread. Top with the tomato slice, followed by the steak. Finish the sandwich by spooning some of the red onion mixture over the steak, followed by the Roquefort cheese.