On a baking sheet, toss the halved cherry tomatoes with 1 tablespoon of olive oil, salt, and pepper. Spread them evenly on the sheet and roast in the oven for 15-20 minutes, or until they are blistered and caramelized.
While the tomatoes roast, bring a large pot of salted water to a boil. Add the spaghetti and cook according to package instructions until al dente, usually around 8-10 minutes.
Reserve ½ cup of pasta cooking water, then drain the pasta and return it to the pot.
Stir in the basil pesto, the remaining tablespoon of olive oil, and balsamic vinegar, mixing until the pasta is well coated. If the pasta seems too dry, gradually add the reserved pasta water until you reach the desired consistency.
Gently fold in the roasted tomatoes, and then sprinkle in the grated Parmesan cheese, stirring to combine. Adjust seasoning with more salt and pepper if needed.
Serve hot, topped with extra Parmesan cheese and fresh basil leaves for garnish.
Notes
Feel free to use homemade pesto for a fresher taste.