1 1/2 pounds pork tenderloin, cut crosswise into 1/2-inch-thick slices
1 tablespoon ground cumin
1 tablespoon kosher salt
1 teaspoon lime zest plus 2 tablespoon fresh lime juice
1 teaspoon finely chopped garlic
1 1/2 teaspoons black pepper, divided
2 teaspoons finely chopped peeled fresh ginger, divided
2 tablespoons coconut oil, divided
1/4 teaspoon black or brown mustard seeds
1 cup thinly sliced red onion
1 1/2 tablespoons thinly sliced serrano chile
3 mangoes, peeled and cut into 3/4-inch-thick spears
1 cup hot water 8 ounces uncooked thin rice noodles or vermicelli, cooked according to package directions
Thinly sliced scallions and pickled cucumber slices, for garnish
Toss together pork, cumin, salt, lime zest and juice, garlic, 1 teaspoon black pepper, and 1 teaspoon ginger in a medium bowl. Cover and chill at least 30 minutes.
Heat 1 tablespoon coconut oil in a large skillet over high. Working in 2 batches, add pork; cook until browned on both sides, 4 to 5 minutes. Transfer to a plate.
Wipe skillet clean; reduce heat to medium. Add mustard seeds and remaining 1 tablespoon oil; cook, undisturbed, until small bubbles appear on surface of seeds, about 30 seconds. Add onion and chile; cook, stirring occasionally, until softened, about 5 minutes. Add mango and remaining 1 teaspoon ginger; cook, stirring gently, until mango is just tender, 6 minutes. Transfer to plate with pork.
Return 1 cup mango mixture to skillet; add 1 cup hot water. Bring to a simmer over medium-high; cook, smashing fruit using back of a wooden spoon, until slightly thickened, about 3 minutes. Return remaining mango mixture and pork to skillet. Cook, stirring often, until pork is fully coated with mango mixture.
Serve pork mixture over noodles; garnish with scallions and pickled cucumber.