Cook the bacon in a 12-inch skillet over medium heat for 8 to 10 minutes, flipping once, until deep brown and crisp.
Drain the bacon on paper towels, then crumble it into small pieces once it's cool enough to handle.
Chop the broccoli florets fine, almost rice-sized, using a chef's knife or a food processor pulsed a few times.
Add the chopped broccoli, diced red onion, shredded cheddar, sunflower seeds, and crumbled bacon to a large mixing bowl.
In a small mixing bowl, whisk together the mayonnaise, apple cider vinegar, dijon mustard, erythritol, garlic powder, salt, and pepper until smooth.
Pour the dressing over the broccoli mixture and toss well with a spoon until every piece is coated.
Cover and chill for at least 15 minutes to let the flavors settle before serving. Taste and adjust salt if needed.
Toss once more just before serving and top with any extra bacon crumbles.