Step 1: Bring a large pot of salted water to a boil. Add the pasta and cook according to package directions until al dente. Reserve about 1 cup of pasta water before draining.
Step 2: While the pasta is cooking, heat the olive oil in a large skillet over medium heat. Add the minced garlic and chopped onion and cook until softened and fragrant, about 3-4 minutes. Be careful not to burn the garlic.
Step 3: Pour in the crushed tomatoes and bring to a simmer. Season with salt and black pepper to taste. Reduce the heat to low and simmer for 15-20 minutes, stirring occasionally, to allow the flavors to meld together.
Step 4: Stir in the heavy cream and chopped basil leaves. Simmer for another 2-3 minutes, until the sauce is heated through and slightly thickened.
Step 5: Add the cooked pasta to the skillet with the tomato sauce. Toss to coat the pasta evenly. If the sauce is too thick, add a little of the reserved pasta water to thin it out.