Bring a large pot of salted water to a boil. While that is happening, start the sauce.
Heat olive oil and butter in a large pot over medium-high heat. Add 4 garlic cloves, fennel seed, and a good pinch of crushed red pepper flakes, if using. Season with salt and pepper and cook, stirring occasionally until garlic begins to turn a lovely golden brown, while the spices toast alongside, 3 to 4 minutes.
Add tomatoes, season with salt and pepper, and turn the heat to high. Cook, tossing or stirring occasionally until they burst but don’t turn to total mush (there should be juiciness, but not jamminess), 5 to 7 minutes (it might look thin, that’s okay). Add vinegar and season again with salt and pepper. Remove from heat while you cook the pasta.
Once pasta is cooked to a nice al dente, drain (I like to use a slotted spoon or strainer and leave the water behind) and add to the pot, tossing to coat. Add some pasta water to loosen things up if it needs, and keep tossing and cooking until the pasta is perfectly cooked and the sauce coats each piece.
Remove from heat and spoon into a bowl, shower it with cheese, the remaining clove of garlic, and more pepper.
