Preheat oven to 350°F/175°C. Lay bacon strips on a parchment-lined sheet tray and bake 18–20 minutes until deeply brown and stiff. Prop one end of the tray to drain fat. Cool completely and dice.
To make the dressing, whisk together buttermilk, sour cream, mayo, garlic powder, onion powder, and salt. Finely chop bleu cheese, chop dill and chives and fold in. Taste and adjust salt if needed.
Quarter the iceberg head, remove the core, and strip the inner 3 layers to create a flat valley in each wedge. Cover with a double layer of damp paper towel and freeze for 10 minutes.
Finely dice and rinse the red onion. Seed and small dice the tomato.
Place a chilled wedge in a bowl and sauce generously with dressing. Layer on diced tomatoes, bacon, red onion, additional dressing, chives, dill, and additional bleu cheese.
To plate, spoon dressing on serving plate, set wedge on top.