01 - Using a sharp knife, slice off the tops and bottoms of each orange and grapefruit. Following the curve of the fruit, cut away the peel and white pith. Cut the citrus into thin rounds or supreme into individual segments, collecting any juices.
02 - Halve the avocado, remove the pit, and peel away the skin. Slice the flesh thinly and set aside. Squeeze a touch of lemon juice over the slices to prevent browning.
03 - Peel the red onion and cut it into paper-thin slices. Tear the fresh mint leaves and roughly chop the toasted pistachios or walnuts if using.
04 - In a small bowl, combine the extra-virgin olive oil, fresh lemon juice, honey or maple syrup, and Dijon mustard. Whisk vigorously until emulsified. Season with sea salt and freshly ground black pepper to taste.
05 - Spread the mixed greens across a large serving platter. Artfully layer the citrus rounds or segments, avocado slices, and red onion over the greens.
06 - Scatter the pomegranate seeds and crumbled feta evenly over the arranged salad.
07 - Drizzle the prepared dressing evenly over the entire platter. Garnish with torn mint leaves and chopped toasted nuts if desired. Serve immediately while the greens are fresh and crisp.