Orange marmalade amped up with fish sauce, fresh lime juice, garlic, and ginger makes a delectable syrupy sauce for juicy pork tenderloin.
Bring rice, 1 1/3 cups water, and 1/2 teaspoon salt to a boil in a saucepan. Reduce heat, cover, and simmer until liquid is absorbed, 16 minutes. Remove from heat. Toss watercress with 1 tablespoon oil; season with salt. Add to pan; let stand, covered, 10 minutes. Stir.
Season pork with salt. Heat remaining oil in a large skillet over medium-high. Add half of ginger; cook until golden, 1 minute. Let drain on paper towels. Add pork to skillet and brown, 3 to 4 minutes; remove from pan. Add remaining ginger and garlic to skillet; cook 30 seconds. Add marmalade, fish sauce, and lime juice; bring to a boil, stirring, until syrupy, 1 minute. Return pork to pan; simmer 30 seconds. Serve over rice, with watercress sprigs and crisp ginger.