How to Make It
Combine Swiss, Gruyère, and cornstarch in a large bowl. Mix until cheese is evenly coated.
Rub the inside of a fondue pot with the cut side of the garlic; discard garlic. Add wine to pot and bring to a simmer over medium heat.
Slowly begin adding cheese to the fondue pot. Cook, stirring in a figure 8 motion and adding cheese one handful at a time after the previous handful has melted, until a smooth mixture forms. Stay below a simmer once you begin adding the cheese. Add lemon zest and juice, nutmeg, and cayenne and stir to combine. Season with salt and several grinds black pepper to taste. Lower heat to the warm setting, stirring occasionally. Add a splash of wine to loosen the fondue if it begins to thicken too much.
Serve with dipping accoutrements and fondue sticks or skewers.