ON A TRIP to the Indian state of Andhra Pradesh in February 2017, Sana Javeri Kadri, right out of college and working in marketing at Bi-Rite, San Francisco’s beloved specialty-grocery chain, was introduced to a turmeric so flavorful and nuanced, it changed the direction of her life. That might sound dramatic, but given the dusty old spices she was familiar with, this golden, glowing powder, packed with zesty, floral notes, was nothing short of a revelation. The man behind the bounty was a third-generation farmer, Prabhu Kasaraneni, who had planted heirloom turmeric using ancient, self-taught farming methods among fields of marigolds, bananas, and black rice. Within days, Javeri Kadri decided to put an income-tax return toward purchasing roughly seven hundred pounds of turmeric from him, promising to return to India…