Crisp the bacon in a skillet over medium heat, 7–9 minutes. Drain, cool, and crumble.
Toast sunflower kernels in a dry skillet until fragrant, 2–3 minutes. Cool completely.
Rinse and dry broccoli and cauliflower. Chop into small bite-size pieces and place in a large bowl.
Add red onion, cranberries, and shredded cheddar to the bowl and toss to combine.
Whisk mayonnaise, Greek yogurt, vinegar, honey, Dijon, salt, and pepper until smooth.
Pour dressing over the salad. Toss until everything is evenly coated.
Fold in the crumbled bacon and toasted sunflower kernels just before serving for crunch.
Chill 20–30 minutes to let flavors mingle. Taste and adjust seasoning.