Preheat oven to 400 degrees F. For sauce, in a small bowl combine mayonnaise, pickle relish, and ketchup. In another bowl combine cabbage, vinegar, and caraway seeds.
Slice bread lengthwise. Hollow out some of the bread for sandwich fillings. Spread some of the sauce on cut sides of bread; reserve remaining sauce for serving. Arrange half the cheese slices on bottom half of bread. Top with cabbage mixture, turkey, and remaining cheese. Top with top half of bread. Wrap tightly in foil and place on a baking sheet. Bake for 10 minutes. Carefully unwrap and bake 2 to 3 minutes more until bread is crisp and cheese is melted. Serve with remaining sauce.
To serve, cut loaf in slices with a sharp serrated knife. Pass remaining sauce.