In a small bowl combine the brown sugar, salt and pepper, mix well, then coat the outside of the tenderloins with the dry rub. Make sure to rub all sides of the tenderloin, coat as much of it as possible.
Place the tenderloins in a pan, I love to use a good quality cast iron pan for tenderloins for even heat distribution. You can bend the tenderloins to fit them in perfectly.
Slice onions and shallots and toss in the middle of the pan between the tenderloins. Drizzle with olive oil.
Place pan in the oven and cook for about 15 to 20 minutes, you want the internal temperature to reach approximately 140 to 145 degrees F. Move the onions and shallots around at least once during the cooking process. If you like your tenderloins well done with a crisp outer layer you can leave them in for about 3 to 5 minutes longer. The rub will start to caramelize and crisp the outside of the tenderloins.
Remove from the oven and allow the tenderloins to cool for about 10 minutes before slicing. This allows the juices to redistribute.
If the onions and shallots are golden you can remove them from the pan. If they are not golden, then spread them in the pan in an even layer and place back in the oven for 3 to 5 minutes
Once you’ve allowed the tenderloins to cool for about 10 minutes, you can slice them both thinly. Place on a platter, then top with caramelized onions, shallots and lots of Haskapa Chutney.