For the sauce: In a medium bowl whisk together the creme fraiche, mustard, lemon zest, lemon juice and salt. Cover with plastic wrap and set aside.
For the salmon: Sprinkle the salmon fillets on all sides with the salt. Heat the olive oil in a large oven-proof skillet over medium-high heat. With tongs, gently place the salmon, flesh-side down, in the pan. Allow the salmon to cook, undisturbed, for 3 minutes to form a golden crust. Using a spatula, gently flip each fillet. Transfer the pan to the oven for an additional 5 minutes. Remove from the oven and cover with foil to keep warm.
For the succotash: Heat the olive oil in a medium skillet over medium-high heat. Add the red peppers and shallots and cook for 4 minutes, stirring often with a wooden spoon. Add the corn, edamame and salt and cook for another 3 minutes. Remove the pan from the heat and stir in the kale, basil and lemon juice.
To serve: Spread 2 tablespoons of the sauce in a circle on each serving plate. Top with 1/2 cup of the succotash, and a salmon fillet. Serve with sauce on the side if desired.