Tender corned beef stacked on rye bread with mustard is a protein-packed deli classic with deep, briny flavor. This hearty sandwich is a family-favorite lunch tradition.
Preheat a skillet over medium heat and add 1 tbsp butter, swirling to coat the pan evenly.
Add slices of rye bread to the skillet and lightly toast both sides for about 2 minutes per side, watching carefully to avoid burning.
Warm the corned beef slices in a separate skillet over low heat for 2–3 minutes, turning occasionally to ensure even heating and retain moisture.
Spread yellow mustard on one side of each toasted rye slice, adjusting the amount to your taste.
Stack warm corned beef generously on four slices of rye, then top each sandwich with another toasted slice, press gently, and serve immediately.