TOSS shrimp with butter. Dip shrimp into spice blend; toss to evenly coat both sides.
HEAT heavy skillet on high heat 5 minutes. Add shrimp, in batches; cook 1 to 2 minutes on each side or until shrimp turn pink, stirring frequently to prevent shrimp from burning. (Shrimp will be "crusty" and very dark.) Serve with Cool Lime Sauce.
COOL LIME SAUCE Mix mayonnaise, sour cream, lime juice and lime zest until well blended; cover. Refrigerate until ready to serve.