In a medium bowl, whisk together the white wine vinegar, cider vinegar, and sugar until the sugar is completely dissolved—this takes about 1-2 minutes of whisking. The sugar needs to fully dissolve so the dressing has a smooth, balanced sweetness rather than gritty crystals. Once dissolved, add the Dijon mustard and whisk to combine.

Slowly drizzle the olive oil into the vinegar mixture from Step 1 while whisking constantly—this emulsifies the dressing and creates a cohesive, slightly creamy texture. Once the oil is incorporated, whisk in the honey and minced shallot. Finally, add the sesame seeds and poppy seeds, stirring to distribute them evenly throughout the dressing. I like to let this sit for a minute so the seeds absorb some of the liquid and the flavors meld together slightly.

Place the fresh spinach in a large bowl, then add the toasted slivered almonds and cranberries on top. Pour the dressing from Step 2 over the salad and toss gently but thoroughly with salad tongs or two forks, making sure every leaf gets coated with the vinaigrette. Be gentle with the spinach to avoid bruising the delicate leaves, but ensure the dressing is evenly distributed—I find tossing from the bottom of the bowl upward gives the best coverage without damaging the greens.

Transfer the dressed salad to a serving platter or individual bowls right away. This salad is best enjoyed fresh, when the spinach is crisp and the almonds maintain their crunch—if it sits too long, the greens will begin to wilt and soften from the dressing.