Grate one half of the lemon to measure 1 tsp (5 mL) of zest. Cut the lemon in half; juice the grated half to measure 1 tsp (5 mL) of juice. Cut the remaining lemon piece into four wedges and set aside. Stir the sour cream with the mayonnaise, dill, chives, capers, lemon zest and juice until well combined. Reserve.
Cut the fish into 4 individual portions (if necessary). Season evenly with salt and pepper. Lightly coat each piece of fish in flour, shaking off excess.
Heat butter in a large non-stick skillet set over medium-high heat. Add fish and cook for about 2 min. per side or until it is golden and flakes when gently tested with a fork. Serve each piece of fish with a dollop of the sour cream mixture and a lemon wedge.