Preheat the oven to 375˚F. Sprinkle the tenderloin(s) well with salt and pepper.
Heat a drizzle of oil along with 1 Tbsp butter in a heavy ovenproof skillet set over medium-high heat, and brown the tenderloin(s) on all sides. Slide the pan into the oven and bake for 20 minutes, or until the internal temperature reaches 160˚F.
When the pork is done, set it aside, covered with foil, and add the other tablespoon of butter to the skillet (don’t wash it out!) along with the saskatoons, honey and vinegar. Bring to a simmer, stirring to loosen any browned bits on the bottom of the pan, and cook until the mixture simmers and thickens. Serve the tenderloin topped with the saucy saskatoons.