In a large bowl, whisk together balsamic vinegar, honey, olive oil, dried thyme, salt, and pepper to create a marinade.
Add the chicken breasts to the bowl, ensuring they're coated with the marinade. Let them sit for about 15 minutes to soak in the flavors.
In a large oven-safe skillet, add the sliced red onion, bell pepper, and cherry tomatoes, making an even layer.
Place the marinated chicken breasts on top of the vegetables in the skillet.
Pour any remaining marinade over the chicken and vegetables.
Scatter the minced garlic on top.
Transfer the skillet to the preheated oven and bake for 25-30 minutes, or until the chicken is thoroughly cooked (internal temperature of 165°F or 75°C) and the vegetables are tender.
Once done, remove the skillet from the oven and let it rest for a few minutes.