Preheat the oven to 180°C.
Cut the leek into 1cm thick round pieces. Line a baking dish with these leek pieces, then scatter the green and peas on top. Pour in the stock, then bake in the oven for about 15 minutes, until the vegetables are tender.
Take the baking dish out of the oven. Put the salmon on top of veggies, season with salt and pepper, and scatter the lemon zest over them. Drizzle with lemon juice and olive oil.
Bake for another 10 minutes or so, until the fish has just cooked through.
Serve with fresh herbs scattered on top.