In a wide frying pan over medium heat, add 1 tablespoon of olive oil. Scatter in the panko breadcrumbs and toast for 4-5 minutes, stirring often, until golden and crisp. Season with salt, then transfer to a bowl lined with kitchen paper to drain.

Wipe out the pan and add the remaining 1 tablespoon of olive oil. Add the sliced onion along with a pinch of salt. Cook for 8-10 minutes, stirring occasionally, until softened and golden brown.

Meanwhile, cook the spaghetti according to package instructions until al dente, remembering to reserve a small cup of pasta water before draining.

Once the onions are ready, add the grated garlic to the pan and cook for about 1 minute until fragrant. Then, add the sardines along with chili flakes (if using), gently breaking them up to create a thick sauce.

Toss in the chopped olives, the can of chopped tomatoes, and the drained spaghetti. Pour in a splash of reserved pasta water and mix until well combined.

Finally, stir in the lemon juice and zest, along with the chopped parsley. Serve in bowls topped generously with the crispy breadcrumbs.