Bring a large pan of salted water to the boil and cook the pasta according to the packet instructions.
Meanwhile, heat the oil in a large pan and cook the garlic over a low heat until soft but not brown. Add the chilli powder, cook for 2 minutes then add the tomato paste and cook for 3 minutes, stirring from time to time.
Add the capers, cook for 2 minutes then stir in the chopped tomatoes and remove the pan from the heat.
When the pasta is cooked, drain it well and stir it into the tomato sauce. Stir in the rocket and season with salt and pepper. Spoon onto serving dishes and scatter over the shaved Parmesan.