Grate 1 tablespoon of orange zest, then juice the oranges and the lemon into a bowl.
Sprinkle the sugar in a skillet and cook over medium-high heat until dark amber, about 5 minutes. Remove from the heat and whisk in the vinegar, citrus juices, zest, and the coriander.
Return to medium-heat and boil until thick, stirring, about 5 minutes (If the sugar hardens, it will dissolve as the sauce heats and thickens).
Remove pan from the heat and whisk in the butter. Cover the pan and set aside.
Season the scallops on one side with salt and pepper. Heat oil in a large skillet over medium heat. Add the scallops seasoned-side down and sear until golden, 4 to 5 minutes.
Flip and cook until golden on the other side 3 to 4 minutes.
Serve over cooked rice or quinoa making sure to drizzle the orange sauce over the scallops.