After considering many possibilities, here's what I did with the arugula and the pizza. In summer/fall, I would use fresh tomatoes instead.
1 medium onions, sliced lengthwise
1/4 lb arugula
Salt and pepper to taste
1 14-inch pizza crust
1/2 cup tomato sauce
2-3 oz. crumbled feta
3-4 oz. shredded mozzarella
Preheat the oven to 450 degrees.
Heat a little olive oil in a skillet and add the onions. Saute over low-medium heat, stirring periodically, until brown and very soft. Add the arugula, raise the heat, and saute just until wilted (a minute or less).
Paint the pizza crust with a little olive oil. Spread the tomato sauce over it, then spread the onion and arugula mixture over that. Sprinkle with feta and top with mozzarella. Bake 15-20 minutes, until cheese begins to brown and crust is done.