For the pangrattato, warm the olive oil in a large pan over a medium–high heat.
Add the breadcrumbs and season with salt. Fry for 4 to 5 minutes, stirring occasionally, until golden in colour. Transfer to a small bowl.
Cook the spaghetti in a large pot of generously salted boiling water until al dente. Reserve about one quarter of the pasta cooking water for the sauce.
While the pasta is cooking, prepare the sauce by warming the olive oil in a large deep pan over a low heat.
Gently cook the garlic, chilli and capers until fragrant, for around 3 minutes.
Increase the heat to medium–high and add the lemon juice and zest.
Add the cooked spaghetti and the reserved cooking water to the pan and toss to coat.
Gently stir through the tuna, being careful not to break up the fillets and sprinkle in the parsley.
Season with salt and pepper.
Sprinkle the pasta with plenty of pangratatto and serve with extra chilli and lemon.
