1.Heat a large frying pan over medium-high heat. Add oil, onion and garlic. Cook, stirring, until the onion is translucent. Add rice and stir until coated in onion mixture. Add lemon rind.
2.Meanwhile, heat the stock in a saucepan until simmering.
3.Add the stock to rice mixture by the ladleful, shaking the pan to stir. When the stock is absorbed into the rice, add more. If you need to dislodge grains from the bottom of the pan, stir very carefully with a silicone spatula. Try to avoid stirring as much as possible. Continue adding stock until rice is cooked but not mushy. Taste the rice when it appears to be nearly ready.
4.Add peas a couple of minutes before risotto is ready. Remove from heat and stir in lemon juice. Season. Top with parmesan and serve with rocket salad, if desired