Rinse and dry the fillets. Sprinkle with salt and pepper, then dredge both sides in flour.
In a skillet over medium heat, heat the olive oil and butter together. Fry the fillets until golden and cooked through, about 3-4 minutes per side, depending on how thick your fillets are. Remove to a plate and tent with foil to keep warm.
In skillet over medium heat, swirl ¼ cup butter to melt. Add lemon juice and swirl to incorporate.
Add cilantro. Remove immediately from heat and pour over fish. Serve with lemon wedges (optional).