Step 1

1 Toss together the onion, sugar and a generous sprinkling of salt (about 1 teaspoon) in a medium bowl; let sit for 5 minutes so the onion wilts a bit

Step 2

2 Stir in the vinegar; let sit for 10 minutes so the vinegar infuses the onions, and the sugar and salt have dissolved

Step 3

3 To assemble the sandwiches, top 4 slices of the bread with a thin coating of mustard

Step 4

4 In the following order, layer the turkey, smoked Gouda, some spinach leaves, some onions and the cherries, then top each portion with one of the remaining slices of bread

Step 5

5 Serve immediately, or wrap tightly in plastic wrap and refrigerate for no more than 2 hours before serving