Tear the radicchio into bite-sized pieces and slice the garlic thinly.

Boil water in a pot and cook the spaghetti 1 minute less than the package instructions. Reserve 3 tbsp of pasta water and drain the rest.

Heat olive oil and garlic in a frying pan until fragrant. Add the radicchio and sauté briefly. Then add the spaghetti, reserved pasta water, salt, and pepper. Stir-fry over medium heat for 1 minute.