In a large pot of water with 1 tbsp salt, cook the spaghetti as per instructions on pack. Do not overcook the pasta.
Score the tomatoes lightly with a sharp knife. Cut the bell pepper into 4 large pieces avoiding the seeds.
In a microwave safe bowl, place the tomatoes and bell peppers with 1/4 cup water. Cover with a microwave proof lid and cook for 4-5 minutes.
Once cooled, peel off skins of the tomatoes and bell peppers. Using the liquid in the bowl, blend this to a puree in a blender/mixer. Keep aside.
In a saucepan, heat the butter. Sautxe9 the finely chopped onions and garlic for 4-5 minutes until soft. At this point, lower the flame, add the vodka. It will start sizzling and then settle to a simmer. Allow to simmer for 3-4 minutes, after which you can add the prepared tomato -red bell pepper puree.
Bring this to a simmer. After 4-5 minutes, add the cream, mix well on a low flame. Season with salt, pepper and dried basil. Allow this to come to a gentle simmer.
By this time, the spaghetti will be ready. Using pasta tongs, remove the spaghetti from the pot, drain (do not wash the cooked spaghetti) and add directly to the sauce, tossing well to coat.
Divide the pasta in two warmed dishes, garnish with fresh basil and chopped walnuts. Drizzle a bit of extra virgin olive oil over the pasta and it's ready to serve.