Step 1

Heat the oil in a small saucepan. Add the onion and garlic and cook over moderate. heat, stirring, until softened, about 1 minute. Reduce the heat to low. Add the guava paste and water and cook, stirring, until the paste has dissolved, about 5 minutes. Stir in the soy sauce, ketchup and cayenne. Season with salt.

Step 2

Set the pork tenderloins in a 9-by-13-inch glass baking dish and brush them all over with half of the guava glaze.

Step 3

Light a fire or heat a grill pan over moderate heat. Grill the pork, turning and brushing with the remaining glaze, until browned on all sides and cooked through, about 15 minutes. Transfer the pork to a cutting board, cover loosely with foil and let stand for 10 minutes.

Step 4

In a bowl, mix the cilantro, oil, vinegar, onion, chives, jalapeños and garlic. Season with salt.

Step 5

Thinly slice the pork. Garnish with cilantro sprigs and serve with the salsa.