1. Melt the butter in a skillet over medium-high heat. Add garlic and gently fry until garlic is golden brown. Add the crushed chili.
2. Cut the ham into matchsticks and add to the garlic. Heat gently, then add lemon zest and cream. Simmer uncovered for about 20 minutes.
3. Cook pasta in 6-8 quarts of rapidly boiling salted water until al dente (about 8-10 minutes). Drain, but reserve ¼ cup cooking liquid.
4. In a serving bowl, place the lemon and add the drained pasta. Add salt to taste and, if sauce is too thick, add a little of the reserved pasta cooking water. Serve immediately with Parmesan sprinkled on top and a slice of lemon to squeeze on top.