Cut the broccoli florets into bite-sized 1/2-inch pieces—this size is important because smaller pieces absorb the dressing better and are easier to eat. Thinly slice the red onion, keeping the slices relatively thin so they soften slightly as the salad sits. If your bacon isn't already cooked, cook it until very crispy, then crumble it into bite-sized pieces. Have the pecans toasted and chopped, and measure out the golden raisins.
In a small bowl, whisk together the mayonnaise, white vinegar, and sugar until smooth and well combined. I prefer Hellmann's mayo because it creates a creamier, richer dressing than other brands. Taste the dressing and adjust the vinegar or sugar if needed—it should have a slight tanginess balanced with sweetness.
In a large bowl, combine the broccoli florets, golden raisins, and sliced red onion. Pour the dressing from Step 2 over the vegetables and toss everything together until the broccoli is evenly coated. I like to let the salad sit for at least 15-30 minutes before serving so the broccoli can soften slightly and absorb all those flavors—it's much better than eating it immediately.
Just before serving, fold in the crumbled bacon and chopped pecans from Step 1. This keeps them crispy and prevents them from getting soggy in the dressing. Toss gently to combine and transfer to a serving dish.