Prepare the Dressing: In a small bowl, whisk together the lemon juice, chopped fresh dill, Dijon mustard, salt, and extra-virgin olive oil until well combined. Adjust seasoning with freshly ground pepper to taste.
Combine the Salad Ingredients: In a large mixing bowl, add the cooked lentils, diced red bell pepper, diced cucumber, and finely chopped red onion. Gently toss to combine the ingredients.
Add the Dressing: Pour the dressing over the lentil and vegetable mixture. Toss gently until everything is evenly coated with the dressing.
Incorporate the Feta: Add the crumbled feta cheese to the salad and gently fold it in, being careful not to break the feta too much. Taste and Adjust: Taste the salad and adjust the seasoning with additional salt and pepper if needed.
Chill and Serve: For the best flavor, let the salad sit in the refrigerator for at least 30 minutes before serving to allow the flavors to meld.
Serve chilled or at room temperature as a refreshing side dish or a light main course.
