Wash and pat dry 500 grams of ripe guavas. Cut them into small pieces, removing the seeds.
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 mustard seeds, 1 tablespoon of fenugreek seeds, and 1 tablespoon of asafoetida.
Add the cooled mustard oil to the spice mixture and mix well.
Add the chopped guavas to the spice mixture and mix thoroughly, ensuring that the guavas are well coated with the spices.
Transfer the guava 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 guava pickle is ready to be served. Store it in the refrigerator to extend its shelf life.