Heat 1 teaspoon sesame oil in a large cast-iron or heavy skillet over high heat. Add onions; sauté 1 minute or until wilted. Remove from pan; set aside.
Add remaining 1 teaspoon sesame oil and peanut oil to pan. Pat scallops dry with paper towels; sprinkle with 1/8 teaspoon salt. Add scallops to pan; cook 2 minutes or until golden brown. Turn scallops; reduce heat to medium, and cook 1 minute or until scallops are done. Remove scallops from pan; keep warm.
Add orange juice, mirin, lemon juice, soy sauce, ginger, red pepper, and remaining 1/8 teaspoon salt to pan; bring to a boil. Reduce heat, and simmer 3 minutes. Combine 1 teaspoon water and cornstarch; stir into sauce. Cook 30 seconds or until sauce begins to thicken. Add scallops to pan; toss to coat. Top with onions.