1.    To prepare Kabobs, preheat broiler. Soak twelve 6-inch bamboo skewers in water 10 minutes; drain.
2.    To prepare Caramelized Onion Relish, heat olive oil in a large nonstick skillet over medium heat until hot. Add onions; cook 8 to 10 minutes or until tender and beginning to brown, stirring occasionally. Stir in balsamic vinegar and brown sugar. Cook 5 to 7 minutes or until liquid evaporates and onion mixture browns and thickens, stirring occasionally. Remove from heat and season with salt and pepper; keep warm.
3.    Cut beef steak into 1-1/4 inch pieces. Season meat with seasoning blend. Thread 3 beef pieces onto each skewer, leaving small spaces between pieces. Place kabobs on rack of broiler pan so surface of beef is 3 to 4 inches from heat. Broil 7 to 11 minutes for medium rare (145°F) to medium (160°F) doneness, turning once.
4.    Serve kabobs with relish. Garnish with basil leaves, as desired.