Bring a large pot of salted water to a boil. Add 340 g spaghetti or bucatini and cook until al dente. Reserve 1 cup / 240 ml of the hot pasta cooking water, then drain the pasta.
While the pasta cooks, heat 3 tablespoons extra virgin olive oil in a large skillet over medium heat. Add 1 small onion, finely chopped, ½ teaspoon kosher salt, and ¼ teaspoon freshly ground black pepper. Cook for 4–5 minutes, until the onion is soft and translucent.
Add 5 garlic cloves, minced, and ¼ teaspoon crushed red pepper. Cook for about 30 seconds, just until fragrant.
Reduce the heat to very low. Add 250 g plain hummus, 2 tablespoons fresh lemon juice, 1 tablespoon lemon zest, and ¾ cup / 180 ml reserved pasta water. Whisk until the hummus pasta sauce is smooth and gently warmed. Do not let it simmer.
Add the drained pasta and toss until evenly coated. Add the remaining pasta water 1–2 tablespoons at a time until the sauce is glossy and silky.
Remove the skillet from the heat. Finish with 1 tablespoon finely grated Parmesan cheese, 1 tablespoon finely chopped fresh basil, additional crushed red pepper if desired, and 1 tablespoon extra virgin olive oil.
Notes
Choose smooth hummus: Plain homemade or store-bought hummus both work, but a smooth consistency blends most evenly with the pasta water.Control the heat: Keep the skillet over very low heat after adding the hummus because simmering can make the sauce tighten.Reserve all the pasta water: Hummus thickness varies, so keep the full 240 ml available and add only what the sauce needs.Finish off the heat: Adding the Parmesan after removing the skillet from the heat helps it melt without becoming grainy.