Heat 2 tablespoons of olive oil in a large sauté pan over medium heat. Add the crushed red pepper flakes and minced garlic. Cook for about 30 to 60 seconds, stirring frequently, until fragrant without allowing the garlic to brown.
Add the halved cherry tomatoes. Cook for 8 to 10 minutes, stirring occasionally, until the tomatoes become tender and begin to blister while some still retain their shape.
Pour in the vegetable or fish broth and bring the mixture to a gentle simmer. Add the basil, lemon juice, lemon zest, salt, sugar, and black pepper. Simmer for about 2 minutes, then taste and adjust the seasoning. Transfer the sauce to a bowl.
Pat the cod fillets thoroughly dry with paper towels. Season both sides with salt and black pepper.
Heat the remaining 2 tablespoons of olive oil in a large nonstick skillet over medium to medium-high heat. Once hot, carefully add the cod.
Sear the fish without moving it for about 3 minutes, or until the underside develops a golden crust. Carefully turn each fillet and cook for another 3 to 4 minutes, depending on thickness, until the fish is opaque and flakes easily.
Spoon the warm tomato basil sauce around and over the fish. Let everything heat together for about 1 minute. Serve the Pan-Seared Cod in Tomato Basil Sauce immediately with extra fresh basil or lemon if desired.