Place potatoes and beets in a 3-quart saucepan over medium heat. Add enough cold water to completely cover vegetables, add salt, and bring to a boil. Once water is boiling, reduce heat to a low simmer; do not cover. Cook vegetables approximately 25 minutes or until potatoes and beets are tender. Once done, place potatoes and beets in a strainer to drain water; run cold water over potatoes and beets until cooled.
In a large mixing bowl, combine cooled potatoes and beets, lentils, and apple cider vinegar. Set aside.
In a small bowl, whisk the lemon juice, mayonnaise, Dijon mustard and ground pepper together. Add the mayonnaise mixture to the potato and beet mixture; combine well.
Potato-Beet Lentil Salad can be refrigerated up to 3 days before serving. Serve on top of chopped kale.
Serving size: 1/2 cup, Calories: 185 calories, Fat: 10 grams, Saturated fat: 1.5 grams, Carbohydrates: 17 grams, Sugar: 3 grams, Sodium: 200 milligrams, Fiber: 5.5 grams, Protein: 5.5 grams, Cholesterol: 5 milligrams