Thinly slice the carrots and cucumber using a mandoline, peeler, or sharp knife. Place the sliced vegetables and thinly sliced red onion in a large bowl.
Whisk together lemon juice, rice vinegar, olive oil, honey (if using), salt, and pepper in a small bowl or jar until emulsified.
Pour dressing over the vegetables and toss gently to coat. Add the chopped herbs and sesame seeds and toss again.
Let the salad sit for 5–10 minutes to allow flavors to meld. Taste and adjust seasoning. Serve chilled or at room temperature, garnished with feta or extra seeds if desired.
Notes
To keep the salad crisp, store sliced vegetables and dressing separately until just before serving.
Try mint or cilantro instead of dill for a different flavor profile.
Add protein like grilled shrimp or shredded rotisserie chicken to make this a light meal.