Stir together cumin, coriander, pepper, paprika, cinnamon, and salt in a shallow bowl. Pat tenderloin dry and dredge in spice mixture until evenly coated.
Heat oil in a 12-inch heavy skillet over moderation high heat until hot but not smoking. Reduce heat to moderate and cook pork, turning occasionally, until meat is browned on all sides. Transfer the pork with tongs to a cutting board and let stand 5 minutes covered.
Meanwhile, discard all the fat from the skillet and add the pomegranate juice to the skillet over medium heat and bring to a boil. Reduce to 2/3 of a cup, about 3 to 5 minutes. Add the wine and heavy cream and boil until the sauce thickens slightly 2 to 3 minutes. Add the sugar if too bitter, season with salt.
Lower the heat and swirl in the butter and add the blackberries. Simmer for a 1 minute.
Slice the pork tenderloin and serve with sauce.