Cook pasta in a large saucepan of boiling salted water following packet instructions until tender. Drain, reserving 1/3 cup pasta water.
Return pan to medium heat. Drain oil from tuna into pan and add tomato and garlic. Cover and cook for 3 minutes or until tomato softens. Add tuna and chilli from can. Flake tuna with a fork and cook for 3 minutes or until heated through.
Stir in zest and lemon juice. Return pasta to pan with reserved pasta water and parsley. Gently toss to combine. Divide between serving bowls, top each with avocado and rocket and serve immediately.