Preheat the oven to 350 degrees. Make lemon butter. Melt 2 Tbsp. butter in a small bowl, then stir/whisk in lemon zest, lemon juice, garlic powder, and a sprinkle of salt and pepper. Set aside. Prepare cod. Brush the cod fillets with 1 Tbsp. olive oil and sprinkle with salt and pepper. Set aside.
Heat 2 Tbsp. olive oil in a cast-iron skillet on medium-high heat. Sear the cod on each side for only 1-2 minutes, then remove from skillet and place on a plate.
Now add shallots, tomatoes, and olives and cook for 2 minutes. Then add garlic, herbs, and a sprinkle of salt and pepper. Cook another 2 minutes. Gently place the cod fillets on top of the mixture and cook in the oven for 15 min. Remove from the oven and pour the butter mixture over each fillet. When ready to serve, divide the cod fillets and tomato/olive mixture onto four plates and spoon the sauce over each portion. Enjoy!