Cook the pasta
Bring a large pot of salted water to a rolling boil. Add the fettuccine and cook according to package directions until al dente. Reserve ½ cup of pasta cooking water, then drain the pasta.

Melt butter and cream base
Return the pot (or use a large skillet) to medium heat. Add the butter and allow it to melt gently. Pour in the heavy cream and whisk just until combined and warmed through, but not boiling.

Season
Add a dash of garlic salt and season to taste with salt and freshly ground black pepper. Taste and adjust.

Incorporate cheeses
Reduce heat to low. Gradually whisk in the Romano and Parmesan cheeses, stirring constantly until the cheese fully melts and the sauce becomes smooth.

Combine with pasta
Add the drained fettuccine back into the sauce. Toss to coat evenly. If the sauce is too thick, add a bit of the reserved pasta water until the desired consistency is reached.

Serve immediately
Serve on warm plates. Top with extra cheese, black pepper, or fresh herbs if desired.