Peel the radish and cut lengthwise like a match stick length but a little thicker than the matchstick. Sprinkle little salt and 1/4 tsp turmeric and keep aside for about half an hour. Water will be released, press more and discard the Water. Add in a bowl.

In the meantime, the radish is macerating, dry roast the sesame seeds and grind it into powder and prepare other ingredients.

In a bowl add in the radish, onion, chillies, cilantro, dry roasted sesame seeds powder, salt as per taste, lemon juice, 1/8 Tsp turmeric powder (this is optional now) and Kashmiri LAL Mirch powder.

Heat mustard oil in a pan and add the fenugreek/ Methi seed. Once it starts crackling and blackening pour the Tempering on top of the ingredients in the bowl and mix it. Wait for few seconds for the hot oil to cool if you are mixing by hand or else use a wooden spoon.
Check salt and sourness, add more salt and lemon juice, if needed.
Serve Fresh but it taste more better after few hours as the flavour infuses so keep it in fridge for few hours. It can last for 2-3 days in the fridge.

You can try this Aloo ko Achaar

See another One with poppy seed also added with sesame

Another with Fresh Cabbage