First, make the crispy tomato skins. Lower the cherry tomatoes into a pan of boiling water for 30-60 seconds until their skins begin to crack and peel, then, using a slotted spoon, lift them into a bowl of cold water. Once cool, peel off the skins and pat dry. Chop the flesh and set aside. Fill a saucepan one-third full with vegetable oil and heat to 170C. Fry the skins for 30-60 seconds or until golden yellow. Transfer to kitchen paper and sprinkle with a little salt.
To make the sauce, bring 50ml water to the boil in a saucepan, add the sugar and stir to dissolve, then cover and put in the fridge to cool down. Once cool, blend with the fish sauce, vinegar and 30g tomato flesh.
Thinly slice the scallops and radishes and mix with the sauce. Transfer the mixture to four plates using a slotted spoon, then drizzle over a bit more sauce and scatter over the tomato skins, dill and chia seeds.