Make the dressing: Whisk the mayonnaise, vinegar, buttermilk and sugar in a small bowl. Stir in the blue cheese and season with salt and pepper. Refrigerate until chilled, about 30 minutes.
Meanwhile, make the glaze: Combine the sugar, balsamic vinegar and 2 tablespoons water in a small nonstick skillet. Bring to a simmer over medium heat and cook, stirring occasionally, until thickened, about 5 minutes. Pour into a small bowl and let cool.
Make the salad: Divide the iceberg wedges among plates. Spoon the dressing on top, letting it run down the sides. Drizzle all over with some of the glaze, about 1 teaspoon per wedge (you will not need all the glaze). Top with the tomatoes, red onion, bacon and blue cheese.
Photograph by Ryan Dausch