Cut onions into quarters; then thinly slice or dice small.

In a large, heavy skillet, heat 2 tablespoons oil over medium heat.

Add onions and cook, stirring often, until golden and very soft, 15-25 minutes.

Reduce heat to medium-low if they start cooking too quickly.

Deglaze pan with balsamic vinegar.

Season to taste with sea salt and freshly ground black pepper.

Remove from heat and fold in arugula.

Sprinkle scallops with salt and pepper.

Heat a second heavy skillet over high heat and add remaining oil; when very hot, add scallops and sear 1-2 minutes per side.

Mound arugula mixture onto plates.

Top with scallops and goat cheese.

Serve with roasted potatoes, quinoa, or brown rice.