So, as with all simple dishes - make sure the few ingredients you get are of good quality. Get a good aged pecorino. The thing is, as simple as it sounds, it can bit a bit tricky to get this sauce right. It's all about love and patience with this dish.
You want a creamy sauce that just coats the pasta - ideally with long pasta like spaghetti but I just used what I had. And you want to add the cheese to the pasta a bit at a time, stirring continuously to have the residual heat of the pasta melt the cheese.
There are different ways of doing it - a lot of recipes make a paste with the cheese and water beforehand and mixing it with the pasta. Personally, this comes out better - perhaps more labor intensive, but it's worth it.
80g pecorino cheese, grated
Extra virgin olive oil
Black pepper, freshly ground
Bring a pot of water to the boil, salt it and cook pasta until al dente - you want it slightly more al dente than you'd normally like it because you're going to cook it a bit more afterwards.
Drain the pasta and reserve about 1/2 cup of the cooking liquid.
Return the pasta to the pot, off the heat, now add a bit of cheese, about 1 tbsp of the liquid and stir. And continue this process - you don't want to add all the cheese at once, you want to add it gradually and let it melt and form a creamy sauce with the pasta. You definitely won't need all that liquid, so do stint on it. At the end, add pepper to taste, a drizzle of olive oil and you're done.