Fill a bowl with ice; add enough salted water to make an ice bath. Bring a large pot of lightly salted water to a boil. Cook the bitter melon in the boiling water until tender yet firm, about 2 minutes; strain the melon. Place the melon into the ice bath; allow to sit until bitterness is extracted, about 1 hour. Drain melon.
Whisk 1 teaspoon soy sauce, 1 teaspoon cornstarch, and baking soda together in a bowl. Add beef and toss to evenly coat. Marinate in the refrigerator for 1 hour.
Heat wok, or a large skillet, on high until smoking. Add 1 tablespoon oil. Lay beef evenly across the bottom of the wok; cook until browned, about 2 minutes per side. Remove beef. Pour in 1 teaspoon of oil; allow to heat. Add onion, garlic, and ginger; cook and stir until fragrant, about 30 seconds. Stir in bitter melon; cook until combined, about 1 minute.
Stir black bean sauce into melon mixture. Stir in remaining soy sauce, oyster sauce, and sugar. Pour in 3/4 cup water; cover and let simmer until flavors combine, 2 to 3 minutes. Uncover and mix in remaining cornstarch and 1 teaspoon water and stir until thickened.
