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 segments, and set aside.
02 - Halve the avocado, remove the pit, and peel away the skin. Slice the flesh thinly and set aside.
03 - Peel the red onion and cut it into thin, even slices.
04 - In a small bowl, whisk together the extra-virgin olive oil, fresh lemon juice, honey or maple syrup, and Dijon mustard until fully emulsified. Season with sea salt and freshly ground black pepper to taste.
05 - Arrange the mixed greens on a large serving platter. Layer the citrus segments, avocado slices, and red onion evenly over the greens.
06 - Scatter the pomegranate seeds and crumbled feta cheese over the assembled salad.
07 - Drizzle the prepared dressing evenly over the salad. If desired, garnish with torn fresh mint leaves and chopped toasted pistachios or walnuts. Serve immediately.