Preheat the air fryer to 190°C. Peel the potatoes and dice into pieces around 5cm in length. Place in a pan filled with cold water and add plenty of salt.
Bring the pan up to the boil and cook for 5-8 minutes, until they start to soften but are still firm.
Drain in a colander and leave them for 5 minutes. After 5 minutes give them a shake to fluff up the edges. Add back into the pan and add 6 tsp of pesto. Toss to coat.
Add the potatoes to the air fryer basket and spray with low-calorie cooking spray. Cook for 20 minutes, making sure to turn halfway.
In a small bowl combine the lemon juice with the remaining 1 tsp pesto. Once the roast potatoes are cooked, drizzle over the lemon juice and pesto and toss to coat.