Peppery Beef Kebabs with Braised Pearl Onions

Name: Peppery Beef Kebabs with Braised Pearl Onions
Ingredients: 60 small white pearl onions (1 pound); 1 tablespoon unsalted butter; 1 tablespoon coarsely ground black pepper; 1 teaspoon finely chopped fresh rosemary; 1 tablespoon minced garlic; 2 teaspoons kosher salt; 1‚ pound (1/2-inch-thick) boneless sirloin steaks, trimmed of excess fat; 20 (4-inch-long) rosemary branches, stripped of all but 1 1/2 inches of top leaves and bottoms cut diagonally to a point; 40 (6-inch) bamboo skewers, soaked in water 1 hour