In a large pot or deep skillet, combine the spaghetti, halved cherry tomatoes, sliced garlic, sliced onion, vegetable broth, olive oil, salt, black pepper, and red pepper flakes.
Bring the mixture to a boil over high heat, stirring frequently to prevent the pasta from sticking.
Once boiling, reduce the heat to medium and continue to cook uncovered, stirring occasionally, until the pasta is al dente and most of the liquid has been absorbed, about 10 to 12 minutes.
Remove the pot from heat and stir in the chopped fresh basil and grated Parmesan cheese until well combined.
Serve immediately, garnished with additional Parmesan and basil if desired.