Put the yogurt in a tea strainer for 10 minutes. Let the water come out from that.
In a wide bowl add the tomato ketchup, yogurt, red chili powder, garam masala, coriander powder, cumin powder, kasoori methi, and salt. As idlis and tomato ketchup has already salt in them, add a little salt.
Make mini idlis and keep them. You can even do this with normal idlis. In that case, you can cut them into four.
Mix the ingredients for marination well and add the idlis, cubed capsicum, and cubed onions to this. Let this marinate for 20 minutes at room temperature.
Wash the skewers or a toothpick put one idli, capsicum, and onion, and repeat the process.
Heat a tawa place the skewers on the tawa and drizzle a few drops of oil on this.
Roll the skewers to get even roasting.
Repeat the same process for the rest of the idlis.
Serve hot.