Toast the nuts. Warm a dry skillet over medium heat. Add the walnuts or pecans and toast for 3–4 minutes, stirring often, until fragrant and lightly golden.
Transfer to a plate to cool so they stay crisp.
Make the dressing. In a small bowl or jar, whisk together olive oil, lemon juice, apple cider vinegar, honey, Dijon, salt, and pepper until smooth and slightly thickened. Taste and adjust. You want a bright, balanced flavor with a gentle sweetness.
Prep the apples. Core the Honeycrisps and slice them thinly.
If you’re prepping ahead, toss the slices with a teaspoon of lemon juice to keep them from browning.
Build the base. Add mixed greens to a large salad bowl. Drizzle with 1–2 tablespoons of dressing and toss lightly to coat. Lightly dressing the greens first helps everything mix evenly.
Add the toppings. Layer on the apple slices, feta, toasted nuts, and red onion.
Scatter the dried cranberries and herbs if using.
Finish and serve. Drizzle more dressing over the top (you may not need all of it). Toss gently to avoid bruising the greens and breaking up the apple slices. Taste and season with a pinch more salt or pepper if needed.
Serve right away.