Season fish with salt and pepper. Dredge in flour; shaking off excess. Heat oil in large skillet on medium. Fry fish 2 to 3 min. per side, or until golden brown and flakes easily with a fork. Transfer to plate and keep warm.
Add butter to skillet (still on medium heat), swirling skillet until butter stops frothing and turns a light brown colour; 1 to 2 min. Remove from heat, stir in capers and lemon juice. Pour butter sauce over fish.
Meanwhile, cook chard in simmering salted water just until tender, 30 sec. to 1 min. Drain and serve alongside fish.