How to Make It
To make the rarebit mix, combine the Guinness, mustard, Worcestershire sauce, Tabasco and egg in a bowl. Add the grated cheese and mix well. Lightly toast the sourdough bread and spread the rarebit mixture on top. Place under a hot grill [broiler] until golden brown, then transfer to an oven heated to 180°C/Gas Mark 4 and bake for 3 minutes.
Meanwhile, put the tomato halves under the hot grill [broiler] until lightly browned. Serve each slice of rarebit sprinkled with sea salt and coarsely ground black pepper and accompanied by a tomato half.