Cut your Beef undercut into 1 cm sized dice. Keep in a bowl with Ginger Garlic Paste, Salt and Coconut Vinegar or White Vinegar or Lemon Juice. Mix it well and allow to marinate for minimum 20 minutes. The longer you keep it marinated the more flavor it will have at the end.
Peel and discard the peel of your onion, quarter and slice thin. Peel, smash and chop your garlic. Cut your chilli small and keep the seeds (Remove the seeds if you want less heat) Half your tomato and slice thin. Keep all separate aside.
Add your marinated beef to a cooking pan, heat up and cook on slow heat without oil so that all the liquid comes out (the beef is full of liquids!). That might take about 15 minutes and when most of the liquid is dissolved, stir fry so that the beef get's perfectly cooked. This should help the beef to remain tender as well.
On another hot plate prepare a frying pan with the oil and fry your onions first translucent. Afterward add the garlic, chili and tomato pieces and stir fry for 1-2 minutes before you throw in the Chilli, Turmeric powder and the Pepper.
Mix and stir fry on a slow to medium flame until all ingredients are soft but not overcooked.
At this point you can add your precooked Beef cubes and stir fry the whole content for another 1-2 minutes or until you feel it has cooked enough. The dish should not end up to dry, nor should it soak in lots of oil.
Serve hot or still warm.
Notes
The recipe is with diced filet beef, which will help you to turn the beef chili fry into a favorite as it won't get tough that way and the ginger garlic paste helps to tenderize the smaller meat pieces.You can adjust the heat to your preference by removing the green chili seeds to make it less hot or by adding more chili powder or green chili to make it hotter. My recipe is moderately hot, so to say, it tickles the tongue.