Take one mixing bowl then add in carrot, capsicum, onion, tomatoes, ginger garlic chilli paste, coriander leaves and semolina.
Now add in sour curd, salt and water as per required and mix well and make thick batter from it, now add in cooking soda mix well and keep aside.
Now for making tadka, heat oil in a nonstick pan, add in mustard seeds and wait till it starts slathering then add in urad dal along with curry leaves and cook it for few seconds, now put the tadka in appam batter prepared from veggies and mix well.
Now take one paniyarm pan and heat on medium flame, now put around 1 tbsp batter on pan and cook it till become nice golden brown both the sides.
Take out the appam in a serving plate and serve with coconut chutney or tomato ketchup and enjoy.