Separate broccoli into florets. Slice tender stalks into thin crosswise coins. Bring a 2 qt. saucepan half full of lightly salted water to a boil. Toss in florets and coins and blanch for 30 seconds, then drain quickly and immerse broccoli in a bowl of ice water. Drain again and chill.
Meanwhile, spread pecan halves on a baking sheet and toast at 350°F for 5-7 minutes while you prepare rest of salad.
For the dressing, in a small bowl, whisk together sugar and vinegar. Stir in soy sauce, garlic and pepper. Whisk in oil and mayonnaise until smooth. Set aside.
In a glass serving bowl, combine reserved broccoli, onion slices, pepper matchsticks and raisins. Remove pecans from oven and break in half lengthwise. Just before serving, pour dressing over broccoli mixture and toss to coat ingredients well. Scatter toasted pecans on top.