Bring a large pot of water to a boil. Season the water with salt. Add the pasta and cook, stirring occasionally, until 2 minutes before al dente.
Just before the pasta is done cooking, melt the butter in a large skillet over medium heat. Add the pepper a cook for ~1 minute.
Add 1/2 cup of the pasta water to the skillet and bring to a simmer. Add the pasta and toss until coated in pasta water/butter.
Add the Parmesan/Grana Padano, stirring and tossing the pasta around until the cheese has melted
Remove the pan from the heat and add the Pecorino Romano, stirring and tossing until the cheese melts.
Serve with additional shredded cheese and freshly cracked pepper, if desired.
Notes: Add a little more pasta water if the pasta seems dry.