Hands down, one of my favorite sandwiches in this city is the Salmon Foccacia at L'Express. Pretty much everything at L'Express is solid, but the salmon sandwich is the gold standard. The foccacia bread is fresh and sprinkled with rosemary. The salmon is perfectly cooked and sliced thin. But it's the added caramelized onions and a stellar lemon-caper mayo that truly makes the sandwich standout. The mayo should be bottled and sold on it's own: it's tangy and the capers give the sandwich a nice saltiness that counterbalances with the salmon. Served with killer shoestring fries and a petite salad for $12.95, it's a lunch that will keep you satisfied throughout the day.