In a large bowl, whisk together the balsamic vinegar, barbecue sauce, and Dijon mustard, and season with salt and pepper to taste.
¼ cup balsamic vinegar, ¼ cup homemade barbecue sauce, 1 tsp. Dijon mustard, Sea salt and freshly ground black pepper
Set half the marinade aside in a separate container.
Add the steak to the remaining marinade and refrigerate for at least 1 hour.
1 lb. sirloin steak
Preheat your grill to medium-high heat.
Thread the beef and tomatoes onto wood or metal skewers, alternating between the two.
2 cups cherry tomatoes
Cook the skewers on the preheated grill, turning occasionally and basting with the reserved marinade until the beef reaches the desired doneness.