Heat the oven to 425°F. Pat the tenderloins dry, rub with olive oil, and season all over with salt, pepper and rosemary.
Heat an oven-safe skillet over medium-high heat. Sear the pork 2 minutes per side until browned, then slide the skillet into the oven.
Roast 15–18 minutes, until the thickest part reads 145°F on an instant-read thermometer. Transfer the pork to a cutting board and rest 5 minutes.
Set the hot skillet over medium heat (use a dry towel on the handle). Add the cranberries, maple syrup, water, balsamic, mustard and garlic. Simmer 8–10 minutes, mashing lightly, until thick and glossy.
Slice the pork into 1/2-inch medallions, spoon the warm cranberry glaze over the top, and serve.