Cook spaghetti in water until al-dente. Drain using a sleeve and reserve 1 cup of pasta water.
Cut a few cherry tomatoes into halves and keep the rest whole.
Heat olive oil in a large pan. Add chopped garlic and chili flake. Cook it on low heat for 1 minute until the oil is aromatic but the garlic is not browned.
Add cherry tomatoes to the pan. Cook on medium heat. When the whole tomatoes soften, season with 1/2 teaspoon of salt. Smash whole cherry tomatoes with the back of a spatula to burst them open. ( Caution: few tomatoes might burst open and splatter. So be careful and maintain distance)
Cherry tomatoes might have cooked at the end of 8-10 minutes and made a thick sauce. Add 1/2 cup of reserved pasta cooking water, cook for a minute, and let the cherry tomato sauce comes to a slow bubble.
Add sugar and more salt if required ( remember pasta cooking water does have salt in it). Lower the heat, and cook spaghetti. Toss well to coat the pasta well with the sauce.
Take the pan off the heat. Add roughly torn fresh Italian basil and parmesan. Toss well to mix.
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Notes
Sugar is optional. It is added to balance the sourness of tomatoes.