The flowers resemble the orchids and the color varies from pink-white to light mauve-purple. At the time I saw it, leaves were dropped (deciduous during the dry season), only the flowers, some 10 to 12 cm in diameter were on trees. Common names include Mountain Ebony, Camel's foot, Orchid tree, Kanchanara (Sanskrit), Kachnar (Hindi). I apologise to the mission "Wild Orchids" - this is not an orchid, obviously, but its resemblance motivated me to post it there as well. When I first saw I was really puzzled - I could not access the tree (too steep) but seeing through the zoom of my camera lens I was confused.
Dry steep hilly areas east of Kathmandu (district of Ramechap) - very dry area receiving rains during monsoon season April to August. This flowers flowered just before rains - while I was around, they received first rains in this season 2017.
The following text was forwarded to me by a friend, Mme Sophie Barre when she helped me identify the species: "Even during ancient times, Koiralo was used in Ayurvedic and herbal medicine to cure many ailments such as treatment of digestive disorder, skin disease, treatment of cough, thyroid problems, improve appetite and treatment of hemorrhoids. Ongoing studies show that the edible flower is packed with full of nutrients." The parts used are flower, bark and roots. "The purple orchid-like flowers have a long history as an exotic delicacy among Nepalese, the food writer and executive chef, Sandeep Khatri in Friday Weekly writes, "The flower is named for Sir Henry Blake, British Governor of Hong Kong from 1898 to 1903, who was a keen amateur botanist by S. T. Dunn, Superintendent of the Botanical and Forestry Department, who assigned it to the genus Bauhinia and named it after Blake in his paper in 1908. This flower was said to have first been discovered in 1880 near the ruins of a house on a shoreline of a western Hong Kong island near Pok Fu Lam. However, this flower and its tree which both have medicinal value have been used in Nepal for centuries."