In a large bowl, combine 3 tbsp olive oil, half of the lemon juice, salt, black pepper, and Italian seasoning.
Add the chicken breasts and coat them well in the seasoning mixture.
Heat the remaining 1 tbsp olive oil in a skillet over medium heat.
Cook the chicken for 6–8 minutes per side, or until golden and cooked through to 165°F (74°C).
While the chicken cooks, mix the chopped tomatoes, garlic, basil, remaining lemon juice, salt, and black pepper in a bowl.
Place one slice of mozzarella over each chicken breast.
Cover the skillet and cook for 2–3 minutes, or until the mozzarella melts.
Transfer the chicken to a serving plate.
Spoon the tomato topping over the chicken.
Finish with freshly grated Parmesan and serve warm.