Start by preparing the sea bass. Rinse the fillets under cold water and pat dry with a paper towel. Place them in a bowl.
In the bowl with the fish, add soy sauce, black pepper, salt, and ginger. Gently toss the fillets to coat them in the marinade. Let them marinate for about 10 minutes.
While the fish is marinating, heat the vegetable oil in a large frying pan over medium-high heat.
Add the sliced onions to the pan and sauté for 3-4 minutes until they become soft and translucent.
After marinating, remove the sea bass from the bowl, allowing excess liquid to drip off. Sprinkle cornflour over both sides of the fish fillets.
Push the onions to the side of the pan and add the marinated sea bass fillets. Cook for about 3-4 minutes on each side, or until the fish is golden brown and cooked through.
Once cooked, drizzle the sesame oil over the fish and onions, tossing lightly to combine.
Transfer to a serving plate, garnish with fresh coriander if desired, and serve with lemon wedges on the side.