Heat 2 teaspoons oil in a large nonstick skillet over medium heat. Add sliced fennel; cook, stirring occasionally, until lightly browned, about 6 minutes. Stir in beans, tomatoes and wine. Cook, stirring occasionally, until the tomatoes begin to break down, about 3 minutes. Transfer to a bowl; stir in chopped fennel fronds, mustard and 1/4 teaspoon pepper. Cover to keep warm.
Meanwhile, combine fennel seeds and the remaining 1/4 teaspoon pepper in a small bowl; sprinkle evenly on both sides of salmon.
Wipe out the pan. Add the remaining 3 teaspoons oil to the pan and heat over high heat until shimmering but not smoking. Add the salmon, skinned-side up, and cook until golden brown, 3 to 5 minutes. Turn the salmon over, cover and remove from the heat. Let stand until the salmon finishes cooking off the heat, 3 to 5 minutes more. Transfer the salmon to a cutting board and flake with a fork. Serve salmon on top of the warm bean mixture.
To skin a salmon fillet: Place it on a clean cutting board, skin-side down. Starting at the tail end, 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 degree angle, separating the fillet from the skin without cutting through either.