Toss together the fresh broccoli florets, shredded cheddar cheese, chopped red onion, sunflower seeds, and raisins in a large bowl.
Whisk mayo, sugar, and apple cider vinegar in a small bowl until smooth.
Pour the dressing over the broccoli mix and stir until evenly coated.
Transfer into pressure cooker pot, seal lid, cook on low pressure for 3 minutes, then natural release for 5 minutes. Open lid, stir, and chill in fridge for at least an hour.
Notes
Serve chilled for the best refreshing taste. Store leftovers in an airtight container.