Mix pastry and roll out on floured board. Line a 9-inch pie tin.
Combine Cheddar, mozzarella, ricotta, chopped onions, mushrooms and salmon. Spoon into pie shell. Arrange tomato wedges on top in a tight overlapping circular pattern. Sprinkle with herbs, salt and pepper. Bake at 325 degrees F for 20 minutes. Cool 15 minutes before serving.