Trim and slice the fennel bulbs: cut off the tough stalks and remove discolored outer leaves. Slice paper-thin.

Prepare a soaking solution with cold water and lemon juice. Submerge fennel slices for 5 minutes to prevent browning.

Cut the radicchio in half and remove the core. Shred or thinly slice it for bite-sized pieces.

Segment the orange and pink grapefruit by slicing off the ends, removing the peels, and cutting between the membranes.

Arrange the radicchio, fennel slices, and citrus segments artfully on a large serving plate.

Combine olive oil, champagne vinegar, lemon juice, honey Dijon mustard, and salt in a jar. Shake until well-blended.

Drizzle the vinaigrette over the arranged salad and sprinkle with fresh cracked black pepper and fennel fronds.