I was too busy so went to packet lunch at terminal 1 canteen. Yan's fish soup stall has one of the best salmon with rice I ever have. Their salmon fish comes with 2 different sauces, Japanses and black pepper sauce. They also have raw salmon with rice too.
Salmon Fish with Black Pepper Sauce 4.5/5
Yan's Fish Soup
Changi Airport Terminal 1
Basement 1 staff canteen
Nearest MRT: Changi Airport, EW Line