Start by preparing your ingredients. Very finely slice the onion, pepper and half the Parma ham. Finely slice the chilli. Quarter the tomato, cut out the seeds and finely dice the flesh. Finely chop the parsley leaves.
Put the finely sliced Parma ham into a large dry frying pan over a high heat and cook for 5 minutes, or until crispy. Transfer to a double layer of kitchen paper to drain. Cook the taglierini in a large pan of boiling salted water until al dente. Meanwhile, return the frying pan to a medium-high heat with 3 tablespoons of oil. Add the onion, pepper and chilli and cook for a minute or so. Roughly slice the remaining Parma ham and add to the pan, stir in most of the parsley leaves and season lightly with salt and pepper.
Reserving some of the cooking water, drain the taglierini and add to the sauce. Add the lemon juice, diced tomato and a good grating of Parmesan. Toss well over the heat until lovely and glossy, adding a splash of the cooking water to loosen, if needed. Divide between your plates, sprinkle over the crispy Parma ham and add an extra grating of Parmesan. Finish by sprinkling over the lemon zest and the rest of the chopped parsley.