Bring a large pot of salted water to boil (1 litre to 1 tablespoon salt). Cook the pasta until al dente. Drain and rinse well under cold water. Drain and set aside.
Rinse and peel the prawns, reserving the heads and discarding the shells. In a small pot, heat 1 tablespoon oil over medium heat. Add in the prawn heads and shells and sauté until the heads and shells turn orange. Add in the cup of water and bay leaf and bring to a boil. Simmer until the stock has been reduced by half. Drain, discarding the prawn shells, prawn heads and bay leaf, and set the stock aside.
Devein the peeled prawns, drain well and season with salt. Rub the salt gently into the prawns and set aside for 10 minutes. Rinse and pat-dry the prawns with paper towels. Set aside.
In a large saucepan (enough to hold the pasta), heat the remaining tablespoon of oil and the tablespoon of butter over medium heat until the butter is no longer foaming. Add in the chopped onion and sauté for 3 minutes, add in the garlic and chili flakes and sauté for another 2 minutes until fragrant.
Add in the peeled prawns and sauté until the prawns are fully cooked. Remove the prawns and set aside.
Add in the prawn stock and cherry tomatoes. Bring to a boil and deglaze the pan. Simmer until the stock has been reduced by half. Add in the cream and simmer until the sauce has been reduced by 1/3. Stir in prawns, pasta and lemon juice. Season with salt and freshly ground black pepper. Heat gently until the pasta is heated through, plate and serve with lemon wedges on the side.
NOTES
- If you are using peeled prawns, use 1/2 cup of stock (chicken, vegetable etc) in place of the prawn stock.