1. Cook the spaghetti in salted boiling water until starting to soften - Usually between 6-8 minutes.
2. At around 4 minutes into cooking the spaghetti, add 1 x tsp of vegetable oil to a medium heat frying pan, add the tomato paste and cook for a few seconds then add the red chilli, pesto paste and garlic.
3. Cook this out for around 40 - 50 seconds and then turn up the heat, and add the spaghetti with a little pasta water. Then add the king prawns, tear in some basil leaves and coat the spaghetti with the sauce.
4. As the prawns start to turn pink, add the spaghetti, a squeeze of half the lemon and then a small amount of the pasta water. This will loosen the pasta sauce ready for serving.
5. Once the prawns are piping hot, serve and add another squeeze of lemon over each dish.