Clean the sea bream, but leave its head and tail fin on. Make a few sharp knife cuts on its skin, rub it with salt and pepper. Sprinkle it inside and out with lemon juice and zest and let it marinate for 30 minutes.
Lay out a tray out with baking paper. Cut the tomatoes finely, crush the garlic, cut the onion into round slices and add the olives. Pour out all of this on the baking paper, place the sea bream on top and add salt and pepper as desired. Put it to bake for 15 minutes in a preheated oven.
Leave it to cool slightly in the tray and serve.