Bring 3 quarts water to boil in Dutch oven. Fill large bowl halfway with ice and water.
Add broccoli stalks to pot of boiling water and cook for 1 minute. Add florets and cook until slightly tender, about 1 minute. Drain broccoli, then transfer to bowl of ice water and let sit until chilled, about 5 minutes. Drain again, transfer broccoli to salad spinner, and spin dry.
Whisk together dressing ingredients in a medium bowl. Set aside.
In a large bowl, combine broccoli, onion, cranberries, sunflower seeds, and bacon bits. Pour the prepared dressing over and mix well.
Refrigerate for at least one hour before serving.
