In a small bowl, whisk together the balsamic vinegar, olive oil, 6 cloves of minced garlic, black pepper, rosemary, and thyme to create the marinade.
Place the seitan cubes and bell pepper pieces in a large resealable plastic bag or a shallow dish.
Pour the marinade over them, seal or cover, and turn to coat everything evenly.
Marinate in the refrigerator for at least 1 hour, or up to 2 hours, turning occasionally.
While the seitan marinates, prepare the Yogurt-Dill Sauce.
In a small bowl, stir together the yogurt, dill, lemon peel, 1/4 teaspoon (20 ml / 0.7 fl oz) black pepper, and 1 clove of minced garlic.
Cover and chill until ready to serve.
Preheat your grill to medium heat.
Drain the seitan and peppers, discarding the excess marinade. Alternately thread the seitan and pepper pieces onto 8 long skewers, leaving a small gap between each piece for even cooking.
Place the kabobs on the grill rack.
Grill for 10 to 12 minutes, turning occasionally, until the peppers are tender and the seitan is nicely browned and heated through.
To serve, carefully remove the kabobs from the grill and place a cherry tomato on the end of each skewer.
Serve immediately, with the chilled Yogurt-Dill Sauce on the side for dipping.