Mix the za’atar with the olive oil in a small bowl to create a paste. Smear this paste over the cod pieces, ensuring they are well coated. Season each piece of fish with a pinch of salt. Place in a non-reactive container and leave to marinade in the fridge for 30 minutes.
For the relish, place all the ingredients in a bowl and mix well. Do not season the mixture with salt as it will already have a salty taste.
Heat a large frying pan over a medium heat, then drizzle in a generous amount of olive oil.
Fry the cod for about 8 minutes on one side and 3-4 minutes on the other side. The cod should be golden-brown with a nice spice crusting.
Serve the cod with a generous helping of the relish.