1 (1 & 1/4 pound) pork tenderloin, trimmed of silver skin
Salt and ground black pepper
1/3 cup ketchup
1/3 cup seasoned rice vinegar
1 (8 ounce) can pineapple chunks, drained with juice reserved
2 tbsp brown sugar
4 cloves garlic, minced
2 tsp hot chili sauce (such as Sriracha®)
1 tsp soy sauce
1 pinch red pepper flakes
1 tbsp vegetable oil
1 tsp butter
1/4 cup chopped green onion (white part only)
2 tbsp chopped green onion tops
1. Cut tenderloin into 4 pieces. Arrange in a single layer between two sheets of plastic wrap and pound with a meat mallet until each is about 1-inch thick. Generously season with salt and black pepper.
2. Whisk ketchup, rice vinegar, reserved pineapple juice, brown sugar, garlic, hot chili sauce, soy sauce, and red pepper flakes in a bowl. Set aside.
3. Heat vegetable oil in a skillet over high heat. Place pork in pan; reduce heat to medium. Cook until browned on both sides and cooked through, 5 to 6 minutes per side. Transfer to a plate.
4. Return skillet to medium heat. Stir butter into hot pan. When butter melts and starts to brown, stir in pineapple chunks. Cook, stirring, until pineapple is golden brown, 3 to 4 minutes.
5. Stir in ketchup mixture and 1/4 cup green onion (white parts). Reduce heat to low and simmer until garlic and onion have softened, 5 minutes.
6. Return pork to skillet; cook, stirring, until pork is heated through. Garnish with 2 tablespoons green onion tops.