How to Make It
Pat salmon dry with a paper towel; cut into 1-inch pieces. Heat 1/2 teaspoon oil in a nonstick skillet over medium-high heat. Add salmon; cook 1 minute on each side or until lightly browned. Transfer to a plate; set aside.
Heat remaining 1 tablespoon oil in a saucepan over medium heat. Add onion; cook 4 minutes or until soft, stirring occasionally. Add tomatoes and salt; cover and simmer 4 minutes or until tomatoes begin to break down. Uncover; add salmon, fish sauce, and water. Increase heat; bring to a boil. Reduce heat to low; cook 12 minutes.
Add dill and garlic; turn off heat. Ladle soup into serving bowls; sprinkle evenly with pepper. Serve immediately.