
Crisp, golden rye wrapped around melted Swiss, warm corned beef, and well-drained sauerkraut, held together with homemade Russian dressing. Two cheese layers keep the bread crisp and the filling in place.
Squeeze the sauerkraut hard in a towel or with your hands until it's nearly dry. Wet kraut is the main reason Reubens go soggy.
Warm the corned beef and the kraut in the pan before assembling: beef with a tablespoon of water, covered, 1 to 2 minutes; kraut in a dry corner of the pan until steaming. A cold, thick filling won't heat through before the rye burns. Wipe the pan out.
Stack, bottom to top: rye (mayo on the outside face, Russian dressing on the inside face), Swiss, corned beef loosely folded, sauerkraut, Swiss, rye (dressing on the inside face, mayo on the outside face). The two cheese layers keep the bread crisp and, as they melt, hold the kraut and beef in place so the sandwich doesn't slide apart when you flip or cut it.
Spread a thin, even layer of mayo edge to edge on the outside of each slice. Thin is enough; a thick layer turns greasy.
Use medium-low heat and no added fat. Mayo browns faster than butter, and rye scorches more easily than white bread, so keep the heat low.
Cook 4 to 5 minutes with a lid on. The lid traps heat so the cheese starts melting before the bottom gets too dark.
Flip, press gently with a spatula once, and cook another 3 to 4 minutes uncovered, until the second side is deep golden and the cheese is running at the edges.
Rest 1 to 2 minutes before cutting on the diagonal, so the cheese sets and doesn't spill out.
The dressing recipe makes about 1 1/2 cups; two Reubens need about 1/4 cup.