In a large pot or deep skillet, heat olive oil over medium heat.
Add the sliced onion and garlic to the pot and sauté for 2-3 minutes until fragrant and slightly softened.
Add the spaghetti pasta to the pot.
Pour in the diced tomatoes with their juice and the vegetable broth.
Add salt, black pepper, red pepper flakes, and dried oregano to the pot.
Bring the mixture to a boil over high heat.
Once boiling, reduce heat to medium-low and simmer uncovered, stirring frequently to prevent pasta from sticking.
Cook for about 10-12 minutes until the pasta is al dente and most of the liquid has been absorbed.
Remove the pot from heat and stir in the chopped fresh basil and grated Parmesan cheese.
Adjust seasoning with additional salt and pepper if needed.
Serve immediately, garnished with extra Parmesan and basil if desired.