Cook pasta - Bring 3 litres / 3 quarts of water to the boil with the 1 tablespoon of salt. Cook pasta per the packet time minus 1 minute. Just before draining, scoop out ~1 cup pasta cooking water, then drain the pasta.
Sauté aromatics - In the same pot, heat the reserved oil from the tuna cans over medium heat. Add the garlic, anchovies and chilli flakes. Cook and stir for 1 minute.
Toss pasta - Add the pasta, capers and ⅓ cup of reserved pasta water. Toss using 2 spatulas for 2 minutes.
Add tuna - Turn off the heat. Add tuna, parsley, lemon zest, juice, salt and pepper. Toss gently to mix through - try to keep some tuna chunks.
Serve immediately!