In a skillet over medium heat, melt the butter. Stir in walnuts and brown sugar, coating evenly. Cook for 5-7 minutes until golden and caramelized. Transfer to parchment paper to cool.

While walnuts cool, wash and chop apples, removing cores and slicing thinly. Rinse cherry tomatoes and cut in half. Peel and slice cucumber. Place in a large mixing bowl.

Add mixed greens and crumbled feta to the bowl. Toss the ingredients gently.

In a small bowl, whisk together olive oil, apple cider vinegar, and honey. Season with salt and black pepper to taste.

Drizzle the dressing over the salad and toss gently. Top with cooled candied walnuts and serve immediately.