Step 1

Whisk all marinade ingredients together in a bowl. (If there are any large chunks of fruit in the preserves, mash them up a bit with a fork.)

Step 2

Take a look at the tenderloin and if it has a thin and tapered end, fold that end onto itself to make it about the same thickness all the way across. Now cut the tenderloin into 4 equal-sized pieces.

Step 3

Add the 4 pieces to a resealable plastic bag. Pour the marinade into the bag, close it, then transfer to the fridge and marinate for 4 to 6 hours.

Step 4

Heat the oven to 400 degrees F.

Step 5

Take the meat out of the marinade and dab off excess marinade using paper towels.

Step 6

Heat the olive oil in a cast iron pan until shimmering. Add the tenderloin pieces and lightly sear on all sides until lightly browned.

Step 7

Transfer the pan, uncovered, to the oven and cook the meat until it has reached an internal temperature of 150 degrees F.* (15 - 20 minutes; flip the pieces over after 8 minutes). Remove the pan from the oven, transfer the meat to a plate, cover loosely with aluminum foil and let the pork rest for 8 minutes.

Step 8

While the pork is resting, set the pan with the drippings back on the stovetop.

Step 9

Add the minced onion and heat, stirring continuously, until the all the pan drippings are sopped up (about 1 minute).

Step 10

Pour in the apple cider and cook until reduced by about half (about 2 minutes).

Step 11

Stir in thyme, Dijon mustard and butter and cook until thickened a bit.

Step 12

Season to taste with salt.