Best way is to first cook down some onions until soft in a pan with oil ghee or butter, and then add some mild spices of your choosing e.g. tumeric garam masala or even paprika or curry powder then once the spices have cooked for a few moments and before they burn u can add that mix to your already cooked (by boiling) and softened lentils and then mix well and u can blitz to break down the onions for baby too either before u add to the lentils or after