Preheat oven to 400 degrees F. Cut two 16 inch long sheets of parchment paper. On a baking sheet, fold each sheet in half. Place two slices of lemon down and then top with one piece of cod on each parchment, keeping to the left side of each parchment. Then split the olives and tomatoes up between the two, and drizzle with half of the olive oil and lemon juice in each. Top with 1 tsp of butter and 1 rosemary spring each.