Since I buy more lemons than I can use, I often throw away a good many which succumb to rot. So, since sharing a problem is always a good idea, I posed the question to my mom. She opened her fridge and handed me a jar with something yellow greenish in it. Frozen lemon juice!
So the answer is squeeze the lemon and freeze the juice. If you want to use it well, freeze it in an ice tray and that way you can melt one cube at a time! I’m super impressed and shall be trying this solution out at the earliest opportunity.