Place potatoes, water and salt in a microwave-safe dish; microwave, covered, on high until potatoes are tender, 7-9 minutes. Drain. , Meanwhile, toss beef with onion, 2 tablespoons oil and pepper blend. Place a large skillet over medium-high heat. Add half of the beef mixture; cook and stir until beef is browned, 1-2 minutes. Remove from pan; repeat with remaining beef mixture., In a clean skillet, heat remaining oil over medium-high heat. Add potatoes; cook potatoes until lightly browned, 4-5 minutes, turning occasionally. Stir in beef mixture; heat through. Sprinkle with rosemary.