Ingredients

• 3 pints grape tomatoes, halved
• 1/4 cup extra-virgin olive oil
• 1 tsp. white balsamic or white wine vinegar
• 2 garlic cloves, thinly sliced
• 1 Tbsp. plus 1 tsp. dried oregano
• 2 tsp. kosher salt, divided
• 4 pieces thin-sliced skinless, boneless chicken breast, or 2 skinless, boneless chicken breasts (about 1 lb.)
• 1 tsp. freshly ground black pepper
• 10 oz. fresh mozzarella, thinly sliced into rounds
• 1/2 small red onion, thinly sliced into rounds
• 1/2 cup peperoncini (about 3 oz.), thinly sliced crosswise

Instructions

1. Preheat oven to 400°F. Toss tomatoes, oil, vinegar, garlic, 1 Tbsp. oregano, and 1 tsp. salt on an 18x13" rimmed baking sheet.
2. If using skinless, boneless chicken breasts, slice them into 4 cutlets: Holding knife blade parallel to board, cut breast in half, slicing along a long side, to make 2 pieces.
3. Season chicken on all sides with pepper and remaining 1 tsp. salt and 1 tsp. oregano. Nestle chicken into tomato mixture. Roast until chicken is almost fully cooked through and tomatoes are starting to burst, 8–10 minutes. Arrange mozzarella rounds over chicken and tomatoes. Return to oven and roast until cheese is melted and chicken is fully cooked through, 2–4 minutes. Top with onion and peperoncini.