Place a large skillet over medium heat. Add the sunflower seeds and toast for 1-2 minutes until golden brown with a nutty smell. Transfer to a small bowl to cool.
In the same skillet, cook half of the bacon until crispy, flipping as needed. Transfer to a paper towel-lined plate to drain. Repeat with the remaining bacon.
Add the mayo, Greek yogurt, vinegar, sugar, salt, and pepper for the dressing to a mixing bowl. Whisk until smooth. Set aside.
Chop the bacon into small pieces and add it to a large mixing bowl. Then add the broccoli and cauliflower florets, cheddar cheese, red onion, and toasted sunflower seeds. Pour the dressing over everything and gently to until evenly coated.
Store in the fridge until ready to serve or enjoy immediatey.
Notes
This salad can be prepare up to 2 days ahead of time. Keep the dressing and salad stored in separate containers and refrigerate. When you're ready, pour the dressing over the salad and stir until coated.