Add onions, and season lightly with salt and pepper. Cook 30 to 40 minutes, until golden and caramelized, stirring occasionally to prevent onions from sticking to the pan. While the onions are cooking, combine lemon juice with 4 cups cold water in a medium bowl. Core and quarter the pears. Set aside until onions are done.
Drain pears in a colander, rinse under cold water and shake dry.
Add pears to the onions, and stir gently to combine. Season to taste with salt. Cover with plastic wrap, and set aside for 10 minutes. To assemble, place equal amounts of the wheat berry mixture in a ring shape on the outer edges of 4 plates. Place equal amounts of arugula inside each ring of wheat berries.