In a medium saucepan, heat oil over medium heat. Add onion, garlic, basil, oregano, pepper, and a pinch of salt; reduce heat to medium-low and cook, stirrring occasionally, 4 minutes.
Stir in tomato paste and cook 3 minutes longer.
Stir in chicken breasts and cook for 1 minute. Add lentils, tomatoes, and their juices, and broth. Bring to a gentle simmer, reduce heat to low, cover and cook until chicken is cooked through, 7 to 10 minutes.
Stir in spinach, cover, and cook 1 minute longer or until spinach wilts. Season with salt and pepper to taste and serve warm.