Preheat the oven to 200°C/400°F/Gas 6 and line a large rimmed, baking sheet with parchment paper or a Silpat® baking mat. Set aside.

Combine red onion, potatoes, and tomatoes in a large glass bowl and sprinkle with the dried herbs. Drizzle with two tablespoons olive oil and season with salt and black pepper, to taste. Toss to coat and spread into a single layer onto the prepared baking sheet.

Add the chicken thighs to the bowl and drizzle with the remaining olive oil. Season with additional salt and black pepper, if desired, and turn to coat. Nestle chicken thighs in between the veggies on the baking sheet and top each with one or two lemon slices. Scatter the remaining lemon slices amongst the veggies on the baking sheet.

Place baking sheet in the preheated oven for 20 minutes. Remove from oven and turn the veggies. Return to oven to roast for another 20-25 minutes, or until the chicken is cooked through.

Food Safety Tip: The safe cooking temperature for chicken is 165°F. Use an instant-read thermometer to test for doneness. Remove from oven when the internal temperature at the thickest part reaches at least 160°F. The temperature will continue to rise several degrees while the chicken rests.

Remove from oven and let chicken rest for 5 minutes before serving. Garnish with fresh herbs, if using, and serve immediately. Enjoy!