Melt butter in a large skillet over medium heat. Add garlic and saute until golden, about 1 min. Add wine and lemon juice and simmer to reduce slightly 30 to 60 seconds. Add marinara sauce, stir and place fish fillets on top. Season with salt, pepper and capers. Cover and cook 4 minutes over medium-low. Turn and cook uncovered an additional minute, or until the fish is cooked through.