Cook together tomatoes, pineapple pieces, a few coriander leaves, curry leaves with 1/2 cup water till they turn soft (6-7 min). Blend the mixture using a hand blender to a smooth paste. To this add green chilli, rasam powder, salt, asafoetida and cooked dal mixed with 3 cups of water.
Boil the mixture on medium heat till the raw smell of rasam powder goes off (15 min).
Switch off the gas, temper and add lime juice.
Top with finely chopped coriander leaves and pineapple pieces.