Heat oil in a large saute pan over medium heat. Add crushed red pepper flakes and garlic and saute for 1 minute, or until garlic is fragrant.
Add the cherry tomatoes and jalapeño and cook, stirring occasionally, until they're soft and blistering, but still hold their shape, about 12 minutes. Add in the vegetable stock, stir, and allow the mixture to come to a light simmer.
Stir in the basil, lemon juice, lemon zest, salt, and pepper and cook for 2 minutes. Transfer the sauce into a large bowl and set aside for later.
Heat oil in the same pan over medium heat. Season both sides of the fish with salt and pepper. Place cod fillets in the oil and cook until golden brown, about 3 minutes on both sides, until it’s cooked through.
Pour the tomato basil sauce over the fish and reheat quickly. Serve all at once with additional chopped basil and rice, or cauliflower rice, or zucchini noodles. Enjoy!