Using a sharp knife, trim the top and bottom of each orange and the grapefruit. Stand fruit on a trimmed end and slice away the peel and pith in vertical strips. Working over a bowl to catch juices, segment each fruit by cutting along either side of the membranes to release clean segments. Reserve any collected citrus juice for the dressing. Place the segments in a medium bowl.

Prepare the fennel and onion

Trim the fennel bulb base and fronds. Thinly slice the bulb crosswise using a sharp knife or mandoline so the slices are almost translucent. If using red onion, halve and slice very thinly. Add fennel (and onion if using) to the bowl with citrus.

Add herbs and greens

Tear the mint leaves if large and add to the citrus and fennel. If using a greens base, arrange the mixed baby greens or watercress on a serving platter or individual plates and mound the citrus-fennel mixture on top.

Dressing

In a small bowl or jar, whisk together the extra-virgin olive oil, fresh lemon juice, reserved citrus juice (about 1 tablespoon), honey, and white wine vinegar until emulsified. Season with sea salt and freshly ground black pepper, tasting and adjusting sweetness or acidity as needed.

Drizzle about two-thirds of the dressing over the assembled salad just before serving, reserving the remainder for anyone who wants extra.

Garnish & Serve

Scatter the toasted pistachios or almonds over the salad for crunch. If using, crumble the feta or shave ricotta salata over the top.

Garnish with a few reserved fennel fronds and a couple extra mint leaves. Serve immediately so citrus remains juicy and crunchy elements stay crisp.