Caramelized Onion Steak Sandwich

1 teaspoon oil (I use flavoured "Chili Oil") 1 large sweet onion , thinly sliced (Walla Walla type) 2 garlic cloves , smashed 1/8 teaspoon cayenne pepper 1[...]

3 tablespoons butter or 3 tablespoons margarine , softened 1 medium sweet onion , sliced and separated into rings 1 teaspoon brown sugar 8 slices pumpernickel[...]