Wash and dry 6 lemons. Turn on the Instant Pot. Pour 1 cup water in the inner pot and place a trivet. Place lemons in a bowl and place on top of the trivet. Close the lid. Set the vent to Sealing position. Hit Manual (High Pressure) for 15 minutes.
In the meantime, roast the spice blend for grinding. Place spices listed under the "Roasting spices list" on a microwave safe plate and heat in microwave for 3 minutes in 30 second increments, stirring in between. Cool for 5 minutes and grind to a fine powder in a spice blender.
Wait for natural pressure release from the Instant Pot. Open lid and remove the lemons. Cut in halves and remove seeds. Turn on the Instant Pot on sauté mode and let it heat up, about 30 seconds. Add oil and mustard seeds. When mustard seeds begin to splutter, add lemons, salt, sugar and all spices. Stir well.
Continue to sauté for 4-5 minutes till the liquid reaches a jam like consistency. Turn off the Instant Pot. For best results, let the pickle rest in the refrigerator for 4-5 days before eating.
Cook time= Time to set for pressure cooking.
For best results, refrigerate the pickle in an airtight container for 1-2 weeks.
Variation: You can use jaggery instead of brown sugar.
Note: The nutrition facts below are my estimates. If you are following any diet plan, I recommend cross-checking with your preferred nutrition calculator.