Cook the tomatoes under a preheated hot grill for 5 minutes until starting to char. Turn the tomatoes over, add the chillies and cook for a further 3 minutes. Turn the chillies over and add the garlic. Continue to cook for 2–3 minutes, turning the garlic once, until softened and charred. Leave to cool slightly, then transfer to a food processor or blender with any juices and the coriander and whizz to a coarse paste. Season and set aside.
Meanwhile, bring the stock to the boil in a saucepan, then reduce the heat and add the clams. Cook for 3–5 minutes until they have opened. Remove from the pan and set aside, discarding any that remain closed. Add the fish to the pan and cook for 2–3 minutes until just opaque, then remove. Add the squid and cook for 1 minute until just cooked through, then remove. Reserve the stock.
Heat the oil in a large frying pan, add the onion and cook for 5 minutes until softened. Stir in the rice, then add the tomato sauce. Pour in the reserved stock (adding 2 times the volume of the rice) and simmer for 12 minutes until most of the liquid has been absorbed.
Arrange the seafood on top of the rice, cover and cook over a low heat for 5–10 minutes until the rice is tender and the seafood is piping hot. Drizzle over the tequila, if using, and scatter over extra coriander and lime wedges.