in a 9 x 13-in baking dish, add the cherry tomatoes, red onion, garlic, olive oil, red wine vinegar, oregano, chili flakes, a good pinch of salt, and black pepper. toss everything together and spread into an even layer
roast for at 425F for 25–30 minutes until the tomatoes are nice and jammy
while the tomatoes are roasting, pat the cod fillets dry, drizzle with olive oil and season both sides with salt and pepper
once tomatoes are ready, remove the dish from the oven and use the back of a wooden spoon to make little pockets in the mixture, add in the cod fillets
roast for another 12–15 minutes, until the cod flakes easily and reaches 145°F internally
spoon some of the tomato juices over the fish
finish with a squeeze of lemon juice and chopped herbs (basil or parsley are great here)
serve with something starchy to soak up the sauce -- i made a simple garlic butter pasta, but crusty bread or rice works too!