Preheat the oven to 200C/180C Fan/Gas 6.Lay the prawns on a double layer of kitchen paper and pat them dry.
Put the cherry tomatoes into a roasting tin large enough to hold them in a single layer and toss in some seasoning and 1½ tbsp of the oil. Roast for 10 minutes.
Cook the pasta in a big pot of boiling, salted water.
Meanwhile, add the garlic to the tomatoes, tossing it around in the juices, and return to the oven for 5-10 minutes. They should be shrunken and slightly caramelised in patches; the garlic should be golden.
Heat 1 tbsp of oil in a large frying pan and sauté the prawns until they turn pink, seasoning and adding lemon juice. Toss in the crab and heat through.
Drain the pasta, return to the pan and add the seafood and the tomatoes, with all the juices from both.
Toss with the parsley and lemon zest, check for seasoning and serve.