Giving me a free piece of meat sets off a chain of events reminiscent of that childhood favorite, If You Give A Mouse A Cookie. I'm not the world's number one consumer of animal flesh, and given that I am also a cook that loves to experiment, you can see how things can get a bit out of hand.
I kept it simple with the gifted pork tenderloin, because I knew its major use would be as a component of something else. And also because *honestly* I don't recall ever cooking one and I didn't feel like looking at recipes. So, a quick season and sear and it was off to the oven...when it came out about 15-20 minutes later, I was pleasantly surprised by the taste. Sure, it was plain, but it was pretty delicious for not having gone through any fancy cider marinating or sweet tea brining. There's a time and a place for that, and my kitchen at Monday lunchtime was not it. In a last ditch effort to add some flavor, I threw sliced onions in the pan for the last sear and then draped them over the pork as it cooked. Not sure it worked, but it did produce beautifully caramelized onions that were awesome on my sandwich!
By the way, chutney mayonnaise almost beats creme anglaise for things you know you shouldn't keep licking but you do anyway.

pork sandwich

1 pork tenderloin
1 onion, sliced
2 pieces good-quality sandwich bread
1 tbsp mayo, preferably homemade
1 tsp Alecia's Tomato Chutney
lettuce

Heat a few tbsps of olive oil over high heat. Season pork tenderloin all over, then sear on each side until brown. After the last turn, add onion slices to the pan, stirring occasionally.
Transfer contents to baking pan and place in 425 oven. Cook for about 15 minutes or until desired temp is reached (use thermometer-I went to 145).
Toast bread. Mix mayo and chutney and spread on one side of bread. Spoon on onions, and top with slices of cooled pork and lettuce.