1. To make sauce: In a medium saucepan over high heat, bring clementine juice, chili powder, and lime zest to a boil. Reduce heat and simmer for 1 hour; mixture should be thickened and syrupy.
2. Remove from heat and whisk in butter, one piece at a time, until incorporated.
3. In a large skillet over high heat, heat 2 Tbsp olive oil until smoking. Season scallops with salt and pepper. Cook 10 scallops 1 to 2 minutes per side, until dark golden brown. Remove to paper towels and drain. Repeat with remaining oil and scallops in 3 batches. Serve scallops hot with warm sauce.