1 1/2 pound rib-eye steak, 2 inches thick salt and pepper, to taste 1/3 cup mayonnaise 3 tablespoons bottled white horseradish olive oil, for sprinkling 1 loaf (1 pound size) crusty bread, thickly sliced and halved 2 tomatoes, thinly sliced 1 bunch scallions, green part only, coarsely chopped
Season the steak with salt and plenty of pepper, pressing and rubbing the seasoning into the meat. Cover loosely and refrigerate for 2 hours or until ready to use.
Prepare a gas or charcoal grill.
In a bowl, stir the mayonnaise and horseradish together with salt and pepper. If the mixture seems too thick, add 1 teaspoon of water. Cover and refrigerate.
When the grill is ready, sprinkle the steak lightly with oil. Grill the steak for 8 to 10 minutes, turning once, or until the meat registers 125 degrees on a meat thermometer for medium rare (cook it a few minutes longer for medium beef). Remove the steak from the grill and transfer it to a cutting board; let it rest for 10 minutes.
Sprinkle the bread with oil and toast it on the grill until golden.
Thinly slice the steak and set half a slice on each piece of bread. Add a slice of tomato, a dollop of the horseradish cream, and sprinkle with scallions. Serve at once.