Heat 1 teaspoon oil in a large nonstick skillet over medium heat. Add sliced fennel; cook, stirring occasionally, until lightly browned, about 6 minutes. Stir in beans, tomato and wine. Cook, stirring occasionally, until the tomato begins to break down, about 3 minutes. Transfer to a bowl; stir in chopped fennel fronds, mustard and 1/8 teaspoon pepper. Cover to keep warm.

Rinse and dry the pan. Combine fennel seed and the remaining 1/8 teaspoon pepper in a small bowl; sprinkle evenly on both sides of salmon. Heat the remaining 2 teaspoons oil in the pan over medium-high heat until shimmering but not smoking. Add the salmon, skinned side up; cook until golden brown, 3 to 6 minutes. Turn the salmon over, cover and remove from the heat. Allow the salmon to finish cooking off the heat until just cooked through, 3 to 6 minutes more. Serve the salmon with the bean mixture.

To skin a salmon fillet, place it skin-side down on a cutting board. Starting at one corner, slip the blade of a long, knife between the fish flesh and the skin, holding the skin down firmly with your other hand. Gently push the blade along at a 30 degrees angle, separating the fillet from the skin without cutting through either.