Prepare the pesto sauce by blending the walnuts, garlic, basil leaves, parmesan cheese and olive oil. It should form a smooth, green paste. Note that the pesto sauce tends to discolor with time so don't prepare it too much in advance.
Drop the pasta in a pot of boiling water to which salt and a little oil have been added.
Stir intermittently to ensure the pasta does not stick.
Cook the pasta al dente (firm but done). Remember that the pasta continues to cook after you toss it with the pesto sauce so it should not be overcooked.
Drain the pasta and keep aside. Do not refresh with water as the starch helps the sauce to coat the pasta.
In a skillet, heat some olive oil and add the cherry tomatoes.
Sprinkle some salt over it and cook with the lid covered.
Once the tomatoes have become soft, take a potato masher or blunt end of the ladle and gently squish the tomatoes (do not turn them into pulp).
Now add in the pesto sauce, chopped walnuts, crushed dry red chillies, salt to taste (if required) and mix. Add the pasta and toss well.
Sprinkle some parmesan cheese and red chilli flakes and serve hot.