For the marinade:
½ teaspoon salt
¼ teaspoon baking soda
¼ teaspoon sugar
1 tablespoon Shaoxing wine
1 teaspoon light soy sauce
¼ teaspoon dark soy sauce
1 teaspoon oyster sauce
½ teaspoon sesame oil
½ clove garlic, grated or smashed to a pulp
1 small red onion, thinly sliced