Combine mayonnaise, tomatoes, garlic, horseradish, ketchup and cayenne in a bowl.

Toss onion, peppers, and pepper flakes together in another bowl. Drizzle with some of the pickling juice from the peppers. Let salad stand for at least 5 minutes.

Spread butter on one side of each slice of bread. Spread mayonnaise on the other side.

Sprinkle cheese on two of the slices. Arrange beef on the cheese, then top with pepper salad.

Place the other slices of bread on the peppers, buttered side up.

Toast sandwiches on both sides using a panini grill.

Tip: If you don't have a panini grill, you can rig something similar. All you need is 2 skillets and a couple of unopened canned goods for weight. One skillet is for cooking and the other is placed on top of the sandwich and weighted down with the canned goods. When the first side is brown, simply flip and put the weights back on.

Grove Tips: first made 1/4/07. We used leftover roast beef, colby jack cheese, and did not have the cherry peppers. I used sweet onion instead of red onion and carmelized them with butter and a touch of sherry.