The saying, "do not underestimate the flavor of simple food" is very appropriate for this side dish. I never used to even give a second thought or even glance when I saw dal fry in buffets or menus in a restaurant. What with all the other lip smacking names like "gobi manchurian", "paneer tikka masala", etc etc vying with each other to capture your undivided attention, truth be told, one can only contemplate the fate of dal fry who looks like "plane Jane" in this context.
"Really??, how did I miss this one?"...this was my reaction after I tasted dal fry for the first time in my life after I had to take care of the leftover food  as part of a get together we had last year at our place... And the other factor was our munchkin loves dal based gravies so much , he relished this dish with gusto, though I had to refill his glass of water as it was quite spicy. Then and there I decided, Dal fry is a must try in my list of experiments to replicate restaurant style food.
So here goes my version where I have tried to get a restaurant style taste for the same:
Thur (toor) dal : 1 cup
Onion medium: 1 sliced thin
Tomato: 2 sliced
Ginger and garlic paste: 1 tspn each
Green chilli : 3 nos slit open (optional, I did not add, but it's really a flavor booster in dal fry according to me)
1tspn each of coriander powder, garam masala powder
1/2 teaspoon cumin powder, turmeric powder, red chilli powder
A pinch of hing
1 tablespoon ghee (or butter, but ghee is best for  the flavor, you can melt the same amount of butter for a minute or two until it forms ghee...or refer my previous posts for making ghee in advance)
Mustard seeds: 1 teaspoon
Cumin seeds: 1 teaspoon
Hing: a pinch
Salt to flavor the ghee
How I made it:
Soak the dal atleast an hour in warm water for faster soaking. It speeds the cooking process and gives a nice buttery texture of cooked dal.
Then in a pressure cooker on medium heat (you may use a plain sauce pan, but it will take an hour to cook the dal well), add ghee, then the tempering ingredients, followed by green chilli,onion, ginger and garlic paste. Stir well until onion turns pink, then add the tomato, spices, and salt. Reduce heat a bit, and stir until the mixture reduces to a paste consistency. It will take around two minutes to achieve that.
Now add the soaked dal along with 4 cups water. Stir again. Check salt and cover pressure cooker. I allow four whistles on my pressure cooker. Switch off heat. Wait for the pressure to completely go away. Then open lid, stir everything well, check salt.
I hope you will try this since it's easy and tasty and healthy. MK