Bring the wine and shallot to the boil in a saucepan. Reduce the heat and add the clams. Cover the pan and cook for 5 minutes until the clams have opened. Discard any that remain closed. Remove from pan with a slotted spoon and leave to cool.
Add the prawns to the pan and cook for 1–2 minutes. Add the scallops and cook for a further 3 minutes, turning halfway through cooking, until the prawns are pink and just cooked through. Set the prawns to one side and slice the scallops.
Whisk together the finely grated rind of the lemon with a good squeeze of the juice, the basil, oil and a little of the seafood cooking liquid. Season and then toss the seafood in half the dressing.
Arrange the tomatoes and salad leaves on serving plates. Place the seafood on top and spoon over the remaining dressing to serve.