Preheat the oven to 200C/400F. Line a large baking tray with tin foil.
Season the fish, inside and out, with salt, pepper, and oregano. Place the lemon slices and fresh dill inside each of the fish cavities.
Place the seasoned branzino on the lined baking tray and sprinkle the dill, cherry tomatoes, and sliced red onion around it.
Roast the branzino for 25-30 minutes, or until the exterior is crispy and fish is cooked through.
Video
Notes
TO STORE: Place leftovers in a shallow container in the fridge. Properly refrigerated branzino keeps well for up to 3 days.TO FREEZE: The cooked and cooled fish can be stored in the freezer in an airtight container for up to two months. TO REHEAT: Reheat branzino in a skillet over medium heat or in the oven preheated to 275F degrees.