Place the tomatoes and soda crackers in the bottom of an 8 x 8-inch (20 x 20 cm) glass dish.
Sprinkle with sugar, basil and salt.
Mix together with a fork.
Set the frozen block of fish over the tomatoes.
Mix together the remaining ingredients and pour over the fish.
Cover with waxed paper.
Microwave at HIGH 8 to 10 minutes, until the fish is well cooked in the center.
Let stand 5 minutes.