Here is a recipe that generations of my family -have been making for ages It's pretty simple and easy and goes very well with dal and rice type of simple Indian meals. You can use limes or lemons, my cousins mother in law gave me a bottle full of this stuff made using lemons from her tree in California.
You need couple of dozens of limes or lemons (you should make it all at one time, bottle it and put it in your pantry). Wash the limes/lemons well and then quarter them (skin and all) and put them in a large bowl. Stir it with salt (2 tbsps) and 1/2 tbsp of ground turmeric (haldi) and pour it all in a glass jar. Cover the jar and keep it in a sunny place (in India we used to always have these pickles basking in the sun). Every morning, shake the jar to ensure the juices that are being released as a result of the salt are evenly distributed within the jar. You keep doing this for a week or so.
Within a week, the lime/lemon will be pretty softened and the salt removes a lot of the bitterness in them. Next you can enjoy them as is or you can season them more.
Here is one way to season them. Make a mixture by stirring some - Sugar or grated Gud (Jaggery) about 1/2 a cup, chili powder (2 tsps), crushed anise seeds (saunf) about 2 tsps and then pour it into the jar and shake some more. Leave it again for a day or so for the flavors to marinate and enjoy the pickle. It will have a delicate sweet, sour, spicy, bitter and pungent taste. You can also add other ground spices if youd like just as ground mustard seeds, ground corrainder seeds etc to it. I like to stick with what I indicated above.
This is a healthier version of preserved lime/lemon pickle. You can also make oil based pickles which are even more pungent but those are easy to buy in a bottle in my humble opinion.