Q- Is there any authenticity in the action stating that Rasulullah (sallallahu ‘alayhi was sallam) used to put salt in his blessed palm and taste it before and after eating?
Haven’t seen a Hadith that clearly states such.
There is an unreliable narration that allegedly encouraged this. “O ‘Ali have salt before and after your meals, for it is a cure for 70 illnesses…”
This has been deemed as a fabrication by the hadith masters and should not be quoted.(Tanzihush Shari’ah, vol. 2 pg.234, also see footnotes of Shaykh ‘Abdul Fattah on Al-Masnu’ pg.236 & Al Yawaqitul Ghaliyah, vol.2 pg.448)
And Allah Ta’ala Knows best
5 Fatwa links are below
https://mawdu.wordpress.com/2017/07/05/salt-before-meals/
https://hadithanswers.com/is-salt-before-meals-a-cure-for-70-illnesses/
https://hadithanswers.com/having-salt-before-meals/
https://darulifta-deoband.com/home/en/Hadith--Sunnah/11425
https://muftionline.co.za/node/2348