If using tomato chutney, mix directly with 1 cup of idli batter.
If using tomato puree heat a teaspoon of oil in a kadai and saute tomato puree for a few minutes until raw smell vanishes.
Use idli batter as such.
Saute spinach leaves in a pan until cooked.
Grind to paste along with coriander leaves.
Mix with 1 cup of idli batter.
Fill idli plates with idli batter (one color per plate).