Prepare the dressing by stirring together the yogurt, mayonnaise, vinegar, honey, salt, and some freshly cracked pepper (about 10-15 cranks of a pepper mill). Set the dressing aside.
Cut the broccoli into very small florets. Place the florets in a colander and rinse with cool water. Let the broccoli drain while you prepare the rest of the salad ingredients.
Peel the carrot, then use a large-holed cheese grater to shred the carrot. Slice the red onion into paper thin strips.
Add the rinsed and well drained broccoli to a large bowl, along with the shredded carrot, sliced red onion, cranberries, and sunflower seeds. Pour the prepared dressing over top, then stir until everything is coated in dressing. Let the salad marinate for 10-15 minutes before serving. Give the salad a brief stir just before serving to redistribute the dressing.