Heat the olive oil in a large pot over medium heat.
Add the chopped onion and sauté for 3-4 minutes until translucent.
Add the minced garlic and cook for 1 minute until fragrant.
Pour in the canned diced tomatoes, vegetable broth, dried oregano, and dried basil. Stir to combine.
Add the dried spaghetti to the pot, pressing it down gently so it is mostly submerged in the liquid.
Bring the mixture to a boil, then reduce heat to medium-low and simmer uncovered for 12-15 minutes, stirring occasionally to prevent sticking, until the pasta is cooked and most of the liquid is absorbed.
Stir in the drained tuna, mixing gently to combine and warm through for 2 minutes.
Season with salt and black pepper to taste.
Remove the pot from heat and sprinkle grated Parmesan cheese over the pasta.
Garnish with chopped fresh parsley before serving.