Bring a large pot of salted water to a boil. Add shells and cook, stirring occasionally, until tender yet firm to the bite, about 9 minutes. Drain and set aside.
Heat olive oil in a large saute pan over medium heat. Stir in onion, red pepper flakes, and black pepper. Cook and stir until onion is soft and translucent, about 3 minutes. Add tomato paste and garlic; cook and stir until fragrant, about 1 minute.
Add tomatoes and balsamic vinegar to the pan with the onion mixture. Bring to a boil and cook, uncovered, until thickened, about 5 minutes. Reduce heat and pour in heavy cream; let simmer for 1 minute. Stir in cooked pasta, Gorgonzola cheese, basil, and salt. Serve immediately.
