Sweet and Sour Fish Fillets

Name: Sweet and Sour Fish Fillets
Ingredients: 4 tablespoons pineapple or orange juice; 1 pound cod fillets, cut into 2-inch chunks; Sea salt and freshly ground white pepper; 1 tablespoon vegetable oil; 2 cloves garlic, minced; 1 teaspoon peeled and grated ginger; 1 red pepper, cut into 1/2-inch chunks; 1 yellow onion, cut into 1/2-inch chunks; One 8-ounce can pineapple chunks in juice; 2 tablespoons rice vinegar; 2 tablespoons light soy sauce; 1 teaspoon brown sugar; 1 heaping tablespoon cornstarch; 1 scallion, sliced, for garnish