For the orange vinaigrette: In a salad dressing shaker, combine the orange juice, vinegar, honey, red onions and olive oil; shake to combine. Season to taste with salt and pepper. Refrigerate until ready to serve. Make sure to shake the vinaigrette once again right before dressing the salad. (Reserve any extra vinaigrette in the refrigerator for up to a week.)
For the salad: In a medium bowl, combine the fennel and radishes, breaking up any pieces that are sticking together. Add the orange supremes, upland cress, pistachios and olives and gently fold the ingredients together. Season with salt and pepper.
Gently toss the salad with vinaigrette and garnish with fennel fronds. Serve immediately.