In an baking sheet, combine the cherry tomatoes, red onion, half the olive oil and half the Herbes de Provence. Season with salt and pepper, and toss to coat evenly.
Brush the chicken breasts with the remaining olive oil and season with the remaining Herbes de Provence, salt and pepper. Nestle the chicken breasts into the vegetables in the bakng sheet.
Place the baking sheet into the hot oven to bake for 15-20 minutes, or until the chicken is thoroughly cooked and the tomatoes are beginning to blacken and release their juices. Remove from the oven and serve immediately.