This America's Test Kitchen recipe is pretty exacting: precise measurements are called for with both the meat and the vegetables. But you know it's gonna be worth it!
1 medium onion, roughly chopped
6 medium garlic cloves, roughly chopped
2 teaspoons finely grated zest
2 tablespoons chopped fresh rosemary
1/3 cup beef broth
1/3 cup vegetable oil, plus extra for cooking grate
3 tablespoons tomato paste
2 teaspoons table salt
1 1/2 teaspoons sugar
3/4 teaspoon ground black pepper
Beef and Vegetables
2 pounds sirloin steak tips, trimmed of excess fat and cut into 2-inch chunks
1 large zucchini or summer squash (about 1/2 pound), ends trimmed, halved lengthwise, and cut crosswise into 1-inch-thick slices
1 large red or green bell pepper, stemmed, seeded, and cut into 1 1/2-inch pieces
1 large red or sweet onion, ends trimmed, peeled, halved lengthwise, core discarded, each half cut into 4 wedges and each wedge cut crosswise into thirds
FOR THE MARINADE: Place all ingredients in blender and process until smooth, about 45 seconds. Transfer ¾ cup marinade to large bowl and set aside.
FOR THE BEEF AND VEGETABLES: Toss remaining marinade and beef in second large bowl. Cover with plastic wrap and refrigerate 1 hour or up to 2 hours, tossing beef after 30 minutes. Meanwhile, prepare vegetables and toss with reserved marinade. Cover and let vegetables marinate at room temperature at least 30 minutes.
Remove beef from marinade and pat dry with paper towels. Tightly thread beef onto two 12-inch metal skewers, rolling or folding meat as necessary to maintain 2-inch cubes. Thread vegetables onto two 12-inch metal skewers, in alternating pattern of zucchini, pepper, and onion.
FOR A CHARCOAL GRILL: About 30 minutes before grilling, light large chimney starter mounded over rim with charcoal (7 quarts, about 120 briquettes). When top coals are partially covered with ash, arrange all coals in center of grill in even layer, leaving 2-inch gap between grill wall and charcoal. Set cooking grate over coals, cover, and heat grate until hot, about 5 minutes.
FOR A GAS GRILL: Turn all burners to high, cover, and heat grill until hot, about 15 minutes.
Place meat skewers in center of grill directly over coals and vegetable skewers near edge of coals but still over fire. Grill beef skewers until well browned, slightly charred, and instant-read thermometer inserted into center of meat registers 125 degrees for medium-rare, 12 to 16 minutes, turning every 3 to 4 minutes. Transfer beef skewers to serving platter, loosely tent with foil, and let rest 10 minutes. Continue to grill vegetable skewers until vegetables are tender and slightly charred, about 5 minutes longer (17 to 21 minutes total), turning every 4 to 5 minutes. Transfer vegetables to platter with beef. Remove beef and vegetables from skewers and serve.