To begin: Dice the tomato into 1cm cubes and place into a large mixing bowl, season liberally with salt and dress with evoo. Toss well and set aside.
Peel and cut the pickling onions into small wedges and add to the tomato. Dice the fennel into 1cm cubes and add to the mix also.
Crush and roughly chop the garlic, pick the sage leaves and add to the other ingredients, add the olives and finely slice the celery. Mix all the ingredients together and set aside.
In another bowl pick 12-15 celery heart leaves season with salt and set aside.
Score the flanks of the fish on both sides and season the fish inside and out. Spoon out a layer of vegetable mix about the same size as the fish on to a large baking tray. Fill the cavity of the fish with the vegetable mix also. Place the fish on top of the vegetables and pour over the remaining vegetable mix, drizzle with a little evoo and bake the fish in a pre-heated oven combi setting 200 °C for 25 minutes.
As the fish cooks pick and finely slice the parsley leaves and add them to the celery heart. Dress with a little evoo mix and set aside.
Once baked place the snapper and vegetables on a large serving platter and top with the celery heart leaves and serve.