Step 1: Preheat your oven to 400°F (200°C). Line a large rimmed baking sheet with parchment paper for easier cleanup.
Step 2: In a large bowl, combine the boneless, skinless chicken thighs, cherry tomatoes, chopped red onion, minced garlic, and fresh herb sprigs (oregano and thyme). Drizzle generously with olive oil and season with salt, black pepper, and a pinch of red pepper flakes (if using).
Step 3: Toss all the ingredients together until everything is well coated. Make sure the chicken and vegetables are evenly distributed with the oil and seasonings.
Step 4: Spread the chicken and tomato mixture in a single layer on the prepared baking sheet. Ensure there's enough space between the ingredients so they roast rather than steam. Don't overcrowd the pan; if necessary, use two sheets.
Step 5: Roast for 25-30 minutes, or until the chicken is cooked through (internal temperature of 165°F or 74°C) and the cherry tomatoes have burst and softened, releasing their juices. The edges of the chicken should be slightly caramelized.
Step 6: Remove the baking sheet from the oven. Discard the herb sprigs. If using, stir in the fresh basil and a squeeze of fresh lemon juice.
Step 7: Serve immediately. This dish is fantastic on its own, but also pairs beautifully with pasta, rice, or crusty bread to soak up all the delicious pan juices.