Ingredients

1 tablespoon extra-virgin olive oil

1 medium Vidalia or other sweet onion, thinly sliced

1 garlic clove, minced

8 ounces (6 cups) fresh spinach, stemmed

1 ounce (1 cup) watercress leaves, coarsely chopped

1/2 avocado, halved, pitted, and peeled

1 cup plain nonfat yogurt, preferably Greek

1 teaspoon finely grated lemon zest

1 tablespoon fresh lemon juice

1/2 teaspoon hot sauce, such as Tabasco

1/4 teaspoon coarse salt

Freshly ground pepper

Crudites (such as spears of English cucumber, peeled baby carrots, and trimmed radishes), for serving

Preparation

Heat oil in a large skillet over medium heat. Add onion, and cook until softened, about 8 minutes. Reduce heat to medium-low, add garlic, and cook, stirring occasionally, until onion and garlic are very soft and golden, about 20 minutes. Add spinach, and cook, tossing often, until wilted, about 4 minutes. Let cool slightly.

Puree mixture in a food processor until smooth. Add watercress, avocado, yogurt, lemon zest and juice, hot sauce, and salt, and season with pepper. Puree until smooth. Transfer to a bowl, cover, and refrigerate for at least 1 hour (or up to 3 days). Stir the dip, and serve with crudites.