Preheat the oven to 200 degrees C. Cook the potatoes in a saucepan of boiling water for about 8 minutes until they are just tender, then drain.
Arrange the potato, eggplant and tomato slices in overlapping rings in a large, lightly oiled roasting tin.
In a small bowl, combine the anchovies with the oil and capers, then season well with pepper (no salt is needed). Pour the mixture over the vegetables. Cover the dish with foil and bake in the oven for 20 minutes.
Arrange the salmon steaks on top of the vegetables, re-cover with the foil and cook for 10 minutes. Remove the foil and cook for a further 10 minutes until the salmon and vegetables are cooked through.
Meanwhile, in a small bowl, mix the mayonnaise with the lemon zest and juice. Serve the mayonnaise with the cooked salmon and vegetables.
Nicely cooked salmon. I used pumpkin instead of potato and it was yum! The eggplant didn't cook through, so be aware of this when you are cooking. It might need more olive oil or to thinly slice the eggplant. Otherwise delish. - 25 Jan 2011