Wilted Spinach Salad with Feta and Olives

This recipe is from the America's Test Kitchen Family Cookbook
2 (5 ounce) bags baby spinach
6 tablespoons extra-virgin olive oil
1 red onion, chopped fine
2 garlic cloves, minced
2 tablespoons fresh oregeno or 1/2 teaspoon dried
1/2 teaspoon salt
1/2 teaspoon pepper
1/4 teaspoon sugar
2 tablespoons fresh lemon juice
4 ounces feta cheese, crumbled
1/2 kalamata olives, pitted and sliced thin

Place the spinach in a large bowl. Heat the oil in a small skillet over medium heat until shimmering. Add the onion, garlic, oregeno, salt, pepper, and sugar, and cook until the onion is soft, about 3 minutes. Off the heat, stir in the lemon juice, then pour immediately over the spinach and toss to wilt. Portion the salad onto individual plates and sprinkle with the feta and olives.