Mix the salt, ground spices, chilli powder, lemon juice, tomato purée, chilli, ginger and garlic in a large bowl and add the squid. Toss to coat evenly, cover and leave to stand at room temperature for 15 minutes.
Heat a nonstick ridged griddle pan over a very high heat. Working in batches, lift the squid from the marinade and sear in the hot pan for 1–2 minutes, then remove from the pan and keep warm while you cook the remaining squid.
Add the red onion and herbs to the cooked squid, toss to mix well and serve immediately.