Preheat your oven to 350˚F.
In a large, high-rimmed and oven-proof skillet (I like to use my wide cast iron pan), heat the olive oil over medium-high heat. Once heated, add the crushed garlic clove and leave to infuse the oil for a minute. Be sure the garlic does not color. Stir in the tomatoes, sugar and salt. Bring the sauce to a gentle simmer, add the basil leaves and cook for 20 minutes.
While the sauce is simmering, cook your pasta according to package directions. Due to its thickness, rigatoni can sometimes look thoroughly cooked even when it is not. Be sure to taste a piece to know when it is done.
After 20 minutes, the sauce should have reduced and thickened. Take the sauce off the heat, remove the garlic clove and stir in the crème fraîche. Taste and add more salt if desired. Using a slotted spoon, transfer the rigatoni directly from the cooking pot to your sauce. Some of the cooking water will transfer with the pasta and that is okay. We want the sauce to be creamy and this will help. Gently stir the pasta into the sauce so that all the pasta and its big holes are smothered in it.
Top with the grated mozzarella and bake in the preheated oven for 5-10 minutes or until you see the mozzarella has melted and the sauce is bubbling. Enjoy while warm with some fresh crusty bread to mop up any sauces left in your bowl!
Often you can substitute sour cream for crème fraîche without any issues. However, when you are adding it to a warm sauce, this is not a good idea. Crème fraîche has a high fat content, about 30%, compared to about 20% fat content in sour cream. This means that sour cream is more likely to curdle when added to warm sauces. Therefore, I highly recommend finding crème fraîche for this recipe. If you cannot but want to still try this recipe, better to substitute with heavy cream. You will miss out on the tangy flavor that crème fraîche provides, but you will still have a delicious dish!