Cook pasta according to package directions. Bring a large pot of water to boil. Season with salt.
Add pasta. Cook for 8-10 minutes or until al dente. Drain excess water. Set aside.
Heat olive oil in a large frying pan over medium-high heat. Add onions, and sauté, stirring occasionally, for 2-3 minutes or until soft and translucent.
Add garlic, and sauté, stirring, for a minute or until fragrant.Add cherry tomatoes and chopped basil leaves. Cook for 2-3 minutes or until tomatoes start to break down.
Stir in pasta. Add parmesan and red pepper flakes (if using). Season with salt and pepper. Toss. Heat through.
Garnish with more basil leaves if you like.