In a large pot, combine linguine, cherry tomatoes, red onions, garlic, red pepper flakes, basil sprigs, 2 teaspoons of salt, and ¼ teaspoon of pepper.
Pour in 4 ½ cups of water to the pot, ensuring that the ingredients are well-submerged.
Place the pot over high heat and bring the liquid to a boil.
Once boiling, use tongs to toss and flip the pasta regularly. Continue cooking for about 9-12 minutes or until the pasta is al dente, and most of the water has evaporated.
Taste and adjust the salt and pepper as per your preference.
Remove the pot from heat, garnish with fresh basil leaves, and drizzle with a bit of olive oil.
Serve hot, topped with freshly grated Parmesan cheese.