After having peeled the asparagus, pepper, zucchinis and spring onions, slice them vertically with a fairly uniform thickness, to help even out the cooking.
Put a little oil in the pan and lightly fry the vegetables. Season with salt, pepper and coarsely chopped basil and set aside.
Wipe the pan with a paper towel and heat again. Cook the amberjack (skin side down) for 4-5 minutes. Turn off the heat and cover the slices with a lid or aluminum foil.
This will allow the heat to rise so that the entire fillet is cooked simultaneously and the fish is moist and tender.
Set the vegetables on the dish and place the lightly salted fillet on top with the skin side up.