1. Cook pasta according to package directions until al dente, omitting salt and fat. Drain pasta, reserving 1/2 cup cooking liquid.
2. While pasta cooks, heat a large nonstick skillet over medium-high heat. Sprinkle salmon with 1/2 teaspoon salt and 1/4 teaspoon pepper. Add 1 tablespoon oil to pan; swirl to coat. Add salmon; cook 3 minutes on each side or until desired degree of doneness. Remove salmon; flake into large pieces.
3. Add remaining 1 tablespoon oil to pan; swirl to coat. Add fennel and onion; sauté 2 minutes. Reduce heat to medium; cook 10 minutes or until mixture begins to brown, stirring occasionally. Stir in tomatoes and wine; cook 2 minutes or until syrupy. Stir in pasta, reserved 1/2 cup cooking liquid, remaining 1/2 teaspoon salt, and remaining 1/4 teaspoon pepper; cook 2 minutes or until slightly thickened. Gently stir in salmon. Top with fennel fronds, if desired.