Fill a large pot with lightly salted water and bring to a rolling boil. Stir in noodles and return to a boil. Cook pasta uncovered, stirring occasionally, until tender yet firm to the bite, 7 to 9 minutes. Reserve about an 1/8 cup of the pasta water and set aside.

Add eggs, cream, and water to bowl; whisk to combine. Season with black pepper.

Heat butter in a large skillet over medium heat. Add Spam or ham and cook until lightly browned, about 3 minutes. Add onion and cook until onion is translucent, about 5 minutes more.