Preheat the oven to 200°C/gas mark 6. Put the potatoes in a large pan of cold water with a lid on and bring to the boil over a medium-high heat. Add the oil to a large non-stick baking tray and put in the oven.
Once the potatoes come to the boil, turn the heat down and simmer for 10 minutes. Drain in a colander and leave to steam for 3 minutes.
Place the potatoes back in the pan and add the lemon zest. Put the lid back on and shake the pan to evenly distribute the lemon zest and slightly rough up the potatoes.
Remove the hot baking tray from the oven and place the potatoes on it. Season and toss in the oil. Roast for 20 minutes, then turn over and roast for another 20 minutes.