In a mixing bowl, combine rice flour, purple cabbage, onion, green chillies, coriander leaves, cumin seeds,and salt.
Gradually add water and knead into a smooth dough.
Add 1 tsp oil tothe dough and knead again. Divide the dough into equal-sized balls. Keep aside.
In the meantime lets make a chutney. Into a mixer jar, add coconut, dry red chillies, garlic, tamarind,salt and little water. Blend to a fine paste.
For the tempering heat oil in a small pan. Add mustard seeds and udad dal. Once they splutter and turn golden, add curry leaves and dry red chilli. Sauté briefly and pour this tempering over the chutney. Mix well.
Heat an iron griddle on medium flame.
Take one dough ball and flatten it evenly on a banana leaf or butter paper to form a thin rotti.
Transfer the rotti onto the hot griddle. and drizzle oil around the edges.
Cook on both sides until golden brown and crisp. Repeat with the remaining dough.
Serve the hot purple cabbage akki rottis with the freshly prepared coconut chutney.