Sweet and Sour Lettuce Salad

½ cup lemon juice

½ cup cider vinegar

½ cup vegetable oil

1 teaspoon Dijon mustard

¼ teaspoon ground black pepper

⅛ teaspoon salt

3 red apples, chopped

3 green apples, chopped

1 (4 ounce) container crumbled feta cheese

5 cups green leaf lettuce, torn into bite-size pieces

5 cups red leaf lettuce, torn into bite-size pieces

Whisk together the lemon juice, vinegar, oil, mustard, pepper, and salt in a large salad bowl, then add the red and green apples and feta cheese. Place the green and red lettuce over the apple mixture. Refrigerate until ready to serve; toss immediately before serving.