How to make it
Combine 2 Tbsp soy sauce and 1 Tsp sugar in medium bowl. Add beef, toss well, and marinate for at least 10 minutes or up to 1 hour, stirring once.
Meanwhile, whisk remaining 2 Tbsp soy sauce, remaining Tbsp sugar, tangerine juice, sesame oil, and cornstarch in medium bowl. Combine tangerine zest, garlic, ginger, black bean sauce, pepper flakes, and 1 Tsp vegetable oil in small bowl.
Drain beef and discard liquid. Heat 1Tsp vegetable oil in 12-inch nonstick skillet over high heat until just smoking. Add half of the beef in single layer, breaking up clumps. Cook, without stirring, for 1 minute, then stir and cook until browned, 1 to 2 minutes.
Transfer beef to clean bowl. Heat 1 tsp vegetable oil in skillet and repeat with remaining beef. Rinse skillet and dry with paper towels.
Add remaining Tbsp vegetable oil to now-empty skillet and heat until just smoking. Add onion and cook, stirring frequently, until beginning to brown, 3 to 5 minutes. Add snow peas and continue to cook until spotty brown, about 2 minutes longer. Add water and cook until vegetables are crisp-tender, about 1 minute. Push vegetables to sides of skillet;
Add zest-garlic mixture to clearing and cook, mashing with spatula, until fragrant, 15 to 20 seconds. Combine zest-garlic mixture with vegetables. Return beef and any juices to skillet and stir to combine. Whisk sauce to recombine, then add to skillet;cook, stirring constantly, until thickened, about 30 seconds. Serve.