Boil the spaghetti in a large pot of salted boiling water until pasta is al dente. Drain but reserve ½ cup of pasta water.
Cube the butter.
In a large bowl, add the cooked noodles, cubed butter, garlic powder, parmesan cheese and reserved pasta water. Toss to combine and allow the heat from the noodles to melt butter and cheese.
Sprinkle with chopped parsley if desired. Serve and enjoy.