The Tarte Flambe is a regional specialty of Alsace, so naturally while we were there we ordered this thin crusted crispy relative of pizza everywhere we could.
The best one we found, from 5 or 6 establishments, was at a bar whose name we never bothered to find out. It's located in old town Colmar, on Rue des Tanneurs just south east of the Grande Rue (a stone's throw from Au Fer Rouge, which is in Michelin and most guide books). Walking from the Grande Rue, it will be on the right; if you get to Rue des Vignerons you've gone too far. Incidentally, if you drove you can park in the large public lots around the University and police station just north of the bar off of Rue du Chasseur.
The guy who runs the place seems like he might also be the owner, as he was there at all hours and every night. He offers Tartes Flabees in something like 10 flavors, ranging from the classic Nature to Chorizo, with other local types like Muenster. We liked the Nature best, which is a classic lightly cheesy Tarte Flambee with beautifully sauteed onions somewhat akin to cippolinis (SP?) and a wonderful pork product between bacon and pancetta. There's a touch of white sauce, perhaps with some type of cream cheese base with a touch of spices like nutmeg. Very tasty. The Meunster tarte was good too, but cheesier and the crust didn't support it as well.
Later in the evening this place fills up with smoking locals, but if smoke bothers you go earlier in the evening as we did on our second visit and it won't be very smokey.