Preheat the oven to 180°C (350°F).
In a large oven-safe pot or Dutch oven, heat the olive oil over medium heat on the stovetop.
Add the chopped onion and sauté for 3-4 minutes until translucent.
Add the minced garlic and cook for another 1 minute until fragrant.
Add the dried penne pasta, canned diced tomatoes (with their juice), dried oregano, dried basil, salt, and black pepper to the pot.
Pour in the vegetable broth and stir to combine all ingredients evenly.
Bring the mixture to a gentle boil on the stovetop.
Once boiling, cover the pot with a lid and transfer it to the preheated oven.
Bake for 20 minutes, then carefully remove the lid and stir the pasta.
Distribute the cubed fresh mozzarella evenly over the pasta.
Return the pot to the oven uncovered and bake for an additional 10 minutes, or until the pasta is tender and the mozzarella is melted and slightly golden.
Remove the pot from the oven and let it rest for 5 minutes.
Garnish with chopped fresh basil leaves and sprinkle with grated Parmesan cheese if using.
Serve warm directly from the pot.