Wash and dry 500 grams of apples. Core and cut them into small cubes.
In a pan, heat 2 tablespoons of mustard oil until it reaches its smoking point. Then, let it cool down to room temperature.
In a separate bowl, mix 1 tablespoon of red chili powder, 1 tablespoon of turmeric powder, 1 tablespoon of fennel seeds, 1 tablespoon of fenugreek seeds, and 1 tablespoon of mustard seeds.
Add the cooled mustard oil to the spice mixture and mix well.
Add the apple cubes to the spice and oil mixture, ensuring that all the apple pieces are well coated with the spices.
Add 2 tablespoons of salt and 2 tablespoons of sugar to the mixture. Mix well.
Transfer the apple pickle to a clean, dry, and sterilized glass jar. Seal the jar tightly and let it sit in a cool, dark place for 3-4 days to allow the flavors to develop.
After 3-4 days, the apple pickle is ready to be served. Store it in the refrigerator to extend its shelf life.