Cook steaks as directed on package, set aside.
In a small bowl, combine mayo, sun dried tomatoes, garlic, horseradish, ketchup and cayenne. Butter one side of each bread slice and spread the mayo mixture on the other side. To each mayo side of bread, evenly distribute cheese, cooked steaks, top with onion/pepper and close sandwich. Preheat a panini press or a skillet over medium high heat. If using a skillet, place the sandwich in the pan and place a weight on top. The weight can be a sandwich press or another skillet weighed down with a heavy food can. Cook about 3-5 minutes per side until browned and heated through. Makes 4 sandwiches.