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. Serve with lemon wedges.