In a medium bowl, combine the diced tomatoes, red onion, basil, balsamic vinegar, garlic, salt, and pepper. Stir well and let it sit for 15 minutes to allow the flavors to meld.
In a separate bowl, mix together the softened cream cheese, sour cream, mozzarella cheese, Parmesan cheese, and olive oil until smooth and creamy.
Spread the cream cheese mixture evenly in the bottom of a serving dish.
Spoon the tomato mixture over the cream cheese layer, spreading it evenly.
Serve immediately with sliced baguette or cover and refrigerate for up to 2 hours before serving for a chilled option.