Carefully remove skin from the pomegranate.
Working over a sieve placed over a bowl to catch the juices, peel away the thick membrane from the seeds and allow the seeds to collect in the sieve.
Set aside 1/3 cup of seeds for garnish.
Press the remaining seeds with the back of a spoon to release about 2 Tbsp juice.
Discard crushed seeds.
Add the olive oil, vinegar, sugar, salt and pepper to the juice.
Whisk until blended.
Peel the oranges and separate into sections.
Remove the stems from arugula.
Slice the onion crosswise.
Add the arugula and red onion, separating the onion slices into rings.
Drizzle the dressing over the salad, then toss to coat evenly.
Garnish with pemegranate seeds.