For the pancakes, place the plain flour and baking powder into a large bowl, add the egg and milk and whisk to make a thick smooth batter. Stir in the crabmeat, shrimps, spring onion and red chilli.
Heat the olive oil in a frying pan and pour in three separate spoonfuls of batter to make three small pancakes. Cook for 2-3 minutes, then turn over using a spatula and cook for 2-3 minutes on the other side. Remove the pancakes from the pan and repeat with the rest of the mixture. Pile the pancakes onto a plate and keep warm.
For the tomato sauce, heat the olive oil in a pan, add the onion and sauté for 3-4 minutes. Add the chilli and fry for one minute. Add the tamarind paste, sugar, cherry tomatoes and vinegar and cook for five minutes. Stir in the coriander.
To serve, spoon the sauce onto serving plates and top with the pancakes.