Brush the tomatoes and onion slices with oil, sprinkle with oregano and season with salt and pepper. Grill the vegetables quickly on both sides until nicely charred.
Toast slices of sourdough in a toaster or under a broiler. Spread a light coating of soft butter on the toast, sprinkle the chopped rosemary on the buttered bread and dust lightly with black pepper.
Make the sandwiches by layering the arugula leaves, grilled tomato and onion on half of the slices of toasted sourdough. Reserve the unfilled bread for the tops of the sandwiches.
Spread the crumbled blue cheese on top of the vegetables and quickly run the open sandwiches under a broiler. Top with another slice of toasted bread and serve.
Copyright Michael Lomonaco 1997