This creamy, spicy dressing is lighter than you think, and full of flavor.
Make dressing: In a medium bowl, place sour cream, mayonnaise, lemon juice, and chili powder; season with salt and pepper. Whisk to combine.
Remove dark outer leaves from each head of romaine, leaving the heart; place leaves in a plastic bag lined with a paper towel, and refrigerate to use later in Chopped Romaine Salad. Slice hearts in half lengthwise. Place one half on each plate; top with dressing. Sprinkle with scallions and serve.