Why fry a teaspoon of dal to start an Indian dish? Some Indian recipes ask the cook to fry a very small quantity of dal, e.g. "3/4 teaspoon of urid dal", at the beginning of cooking a dish which doesn't otherwise contain dal.  Examples here and here, and I have enough examples in my cookbooks to verify that this way of starting a dish is both traditional and not limited to a particular dish.

I made such a dish a week ago (from a Madhur Jaffrey recipe), and I can't say that the browned dal was in any way detectable in the finished food.  So ... what's the point?  Why fry 1-2 tsp of dal like it was a spice?  Is this maybe a way of testing when the oil is hot enough?
In a dry dish - eg lemon rice, or a dish following the thoran pattern - a teaspoon  of urad dal will definitely be noticeable by giving a crunchy element. 

Do not forget that indian recipes tend to use old school spoon sizes for measurement - a random piece of contemporary flatware will not give you a good approximation here.

Washing and soaking the urad dal for an hour or so can be a good idea if you do not know hold old the dal you are getting is (especially if cooking such dishes when not in India) - too crunchy urad dal could turn into a molar menace.