For the soup, position knife blade in food processor bowl; add cucumber, 1 cup yogurt, and next 3 ingredients. Process until smooth; pour into a bowl. Stir in remaining 1 cup yogurt and purple onion. Cover and chill 3 hours.
For the spinach puree, remove stems from spinach; wash leaves. (Do not pat dry.) Place in a large skillet over medium heat; cover and cook 7 minutes or until spinach wilts, stirring occasionally. (Do not add water.) Press spinach between paper towels until barely moist; set aside.
Heat oil in skillet over low heat. Add garlic; saute 2 minutes. Stir in curry powder and cumin. Remove from heat; add the spinach, stirring well.
Position knife blade in food processor bowl; add spinach mixture, broth, yogurt, and salt. Process until smooth. Spoon into a small bowl.
To serve, divide soup among 4 individual bowls. Carefully spoon 9 dollops (about 1 teaspoon each) of spinach puree in a circle on top of each serving; pull the tip of a sharp knife through dollops to make swirl patterns.