In a medium saucepan, add lentils, 1/2 teaspoon salt, and 3 cups water. Bring to a boil and then reduce to a rapid simmer. Cook for 25 minutes or until tender. Don't overcook. Drain and set aside to cool.
While the lentils cool, in a large bowl, whisk together lemon juice, olive oil, dijon mustard, and honey. On top of dressing, add cucumber, feta, parsley and cooled lentils. Stir ingredients to combine and coat with dressing.
Taste and season with salt and pepper as desired. Enjoy immediately or keep covered in fridge for up to 4 days.