First, prepare the vinaigrette. In a small bowl or a jar with a lid, combine the extra virgin olive oil, fresh lemon juice, Dijon mustard, and honey. Whisk vigorously or shake the jar until the dressing is well-combined and emulsified. Season with a pinch of salt and pepper, taste, and adjust if necessary. Set aside.

Next, toast the pistachios. Place the shelled pistachios in a small, dry skillet over medium heat. Toast for 3-5 minutes, shaking the pan frequently, until they are fragrant and lightly golden-brown. Immediately transfer them to a plate to cool completely to prevent burning.

Finally, assemble the salad. In a large salad bowl, combine the spring mix, fresh blueberries, thinly sliced red onion, and crumbled feta cheese. Add the cooled, toasted pistachios.

Just before serving, drizzle about half of the lemon vinaigrette over the salad. Gently toss to combine, ensuring the greens are lightly coated. Add more dressing if desired, serve immediately, and enjoy.