Preheat the oven to 180°C.
Cut the baby aubergines in half, the courgette and bell peppers into chunks, the onion into thin wedges.
Arrange the vegetables in a baking dish. Add the oregano and oil, toss well.
Put the dish in the oven for 20-25 minutes, or until the veggies are tender.
Toss the vegetables, then put the salmon fillets on top, and scatter the tomatoes around the fish. Add a drop of water or white wine and the lemon juice and season with salt and pepper. Slice the lemon and put the slices on top of the fish. Drizzle with some oil.
Cover the dish with foil and put it back in the oven.
Bake for another 10-15 minutes, then remove the foil.
Check the fish - if it’s cooked through, you’re ready to serve. If not, bake for another 5 minutes.