Trim the fat from the pork tenderloin.

In a bowl, combine the soy sauce, peanut butter, crushed red pepper, and minced garlic.

Stir the mixture well until it forms a smooth marinade.

Spread the soy sauce mixture evenly over the entire surface of the tenderloin, ensuring it is fully coated.

Place the marinated tenderloin on a rack inside a roasting pan.

Coat the roasting pan with vegetable cooking spray to prevent sticking.

Insert a meat thermometer into the thickest part of the tenderloin if desired, to monitor the internal temperature.

Bake the tenderloin uncovered in a preheated oven at 375°F (190°C) for 30 minutes.

Remove the tenderloin from the oven and brush it generously with pineapple preserves.

Return the tenderloin to the oven and bake for an additional 10 minutes.

Continue basting the tenderloin frequently with the pineapple preserves during this time.

Bake until the meat thermometer registers 160°F (71°C) for medium doneness.

Remove the cooked pork tenderloin from the oven and let it stand for 10 minutes before slicing.

Slice the tenderloin into medallions and serve.