In a large skillet, brown bacon. Lay on paper towels to cool, then crumble.
Wash and cut up broccoli, then place in a large mixing bowl and add onion slices.
In a separate bowl, whisk together mayo, vinegar, and sugar.
Pour dressing over broccoli and mix to coat.
Add bacon, raisins, cranberries, and seeds.
Mix well and serve. Refrigerate.