Heat 1 tablespoon oil in a heavy, 3-quart saucepan over medium-high heat. Add onion and fennel and cook, stirring occasionally, until lightly browned, 3-5 minutes. Add water and salt and bring to a boil. Stir in quinoa. Cover and cook over medium heat for 5 minutes.

Stir in tomatoes (with liquid). Return to a boil. Cover, reduce heat, and boil gently over medium heat until quinoa is translucent and tender, 6-8 minutes.

Stir in salmon. Cook, uncovered, over medium heat until salmon turns opaque and is cooked through, about 1 minute. (Check and cook an additional minute if needed.) Turn off heat. Stir in dill, lemon juice, and zest, plus remaining 1 tablespoon olive oil. Add salt to taste, if needed.