Cook the Pasta: Bring a large pot of salted water to a boil. Add the pasta and cook according to the package directions until al dente. Drain and set aside, reserving a small cup of pasta water.
Prepare the Sauce: In a large skillet, heat olive oil over medium heat. Add the garlic and onion and sauté until softened, about 3-4 minutes.
Simmer the Sauce: Add the diced tomatoes, grape juice, Italian seasoning, and red pepper flakes (if using) to the skillet. Stir well, and let the sauce simmer for 10-12 minutes until it thickens slightly.
Combine Pasta and Sauce: Add the cooked pasta to the skillet with the sauce. Toss well to coat the noodles in the sauce. If the sauce is too thick, add a bit of the reserved pasta water to thin it out.
Serve: Stir in fresh basil and season with salt and pepper to taste. Serve with grated Parmesan cheese if desired.
