Slice the tomatoes. I like the slices on the thick side. Layer them on the bottom half of the croissant.
Crack some fresh pepper and salt on the tomatoes, to taste.
Drizzle some balsamic reduction on the tomatoes. I am addicted to this stuff. Low calories and totally delish! I bought mine at Whole Foods. I might start carrying it on my blog for those of you who can't find it in stores. It is perfect on salads instead of heavy dressing.