Preheat a non-stick or cast-iron skillet over medium-high heat and add the olive oil. While the pan is heating, gently pat the cod fillets dry using paper towels, then season both sides with salt and freshly ground pepper. Once the oil shimmers but is not smoking, place the cod fillets in the skillet. Cook for approximately 4 to 5 minutes per side until the fish turns opaque and flakes readily with a fork. Transfer the fillets to a warm plate and set aside. Lower the heat to medium, and if necessary, clear the skillet of any residual bits. Introduce the butter to the pan and allow it to melt, swirling the pan occasionally to ensure even melting. Incorporate the lemon juice and finely chopped herbs into the butter, stirring gently to blend the flavors. Taste the sauce and adjust the seasoning with salt and pepper. Finally, spoon the warm lemon-herb butter sauce generously over the cod fillets before serving.