Peel and crush the garlic. Zest the lemon. Juice half and slice the other half into wedges. Tip the garlic and lemon zest into a bowl. Add the breadcrumbs and scrunch together with a pinch of salt and pepper.
Heat 1 tbsp oil in a frying pan over a medium heat. Tip in the lemony breadcrumbs and fry for 2-3 mins till golden and crisp. Tip into a small bowl.
Peel and finely chop the onion. Halve the cherry tomatoes. Finely chop the parsley stalks and roughly chop the leaves. Finely chop the chilli, flicking out the seeds for a milder heat.
Tip the spaghetti into a large pan with a pinch of salt. Pour in enough boiling water to cover. Bring to the boil and simmer for 8-10 mins till al dente (cooked but still with a little bite).
Heat ½ tbsp oil in the frying pan over a medium heat. Gently fry the onion for 6 mins till soft and glossy. Add the chilli, tomatoes and parsley stalks to the pan. Cook for 2 mins till the tomatoes just begin to break down.
Add the lemon juice and the crab meat and stir for 1 min to just heat through. Add a handful of rocket and wilt down slightly. Season generously.
Tumble in the spaghetti and toss through the sauce. Pile onto warm plates and scatter over the crispy lemon breadcrumbs and parsley leaves. Serve with the lemon wedges for squeezing.