Preheat the oven to 400°F. Pat the fish dry with paper towels. Preheat a skillet over medium heat.
Season the cod fillets with 1 tablespoon of salt, 1 teaspoon of oregano, ½ teaspoon of black pepper, red pepper flakes to taste, fresh parsley, and the zest of 1 lemon. Make sure the fish is seasoned well on both sides.
Add butter to a hot skillet to melt, then add in onions with a pinch of salt. Cook until beginning to soften, about 4 minutes, then add in tomato paste. Cook for 2-3 minutes until the color of the tomato paste deepens. Add in garlic, then the remaining seasonings of red pepper flakes, oregano, lemon zest, and capers. Stir often to ensure the garlic doesn't burn, until it is fragrant, about 1 minute.
Add in the crushed tomatoes, followed by fresh parsley and basil. Stir to wilt slightly for 2-3 minutes, adjusting seasonings to taste.
Nestle in the cod fillets, then drizzle olive oil and half of the lemon juice over top of the mixture. Roast for 20-25 minutes, or until the cod reaches an internal temperature of 145°F and flakes easily with a fork. Squeeze the rest of the lemon juice on, then top with lemon wedges, more fresh parsley, and basil.
Serve hot, spooning the tomato sauce over the cod fillets. Serve it with a nice glass of white wine, like sauvignon blanc or pinot grigio, and some crusty bread.
Store in an airtight container in the fridge for up to 3 days. We don't recommend freezing, as this will alter the texture of the cod.