Wash the Honeycrisp apples under cool water, slice them evenly into thin wedges or cubes, and set aside in a large bowl. Soak thinly sliced red onion rings in a bowl of ice water for about 10 minutes.

In a dry skillet over medium heat, add the pecans and toast for 2-3 minutes, stirring frequently until fragrant and lightly golden. Remove from heat and let cool.

In a medium bowl, combine the olive oil, apple cider vinegar, honey, and Dijon mustard. Whisk until well blended and emulsified. Season with salt and pepper.

In the large bowl with the apple slices, drain the soaked red onion and add it to the mix. Sprinkle in the crumbled feta and toasted pecans. Gently toss to combine.

Drizzle the vinaigrette over the salad and toss gently to coat. Serve immediately, optionally garnished with fresh thyme leaves.