Bring 2 quarts water to a boil in a Dutch oven. Add fresh spinach, and cook for 1 minute. Drain well. Place spinach on several layers of paper towels; squeeze until barely moist.
Heat oil in a medium nonstick skillet over medium heat. Add onion and garlic; cook 6 minutes or until onion is tender, stirring occasionally.
Remove from heat; stir in spinach and salt. Cool to room temperature.
Combine spinach mixture, plain yogurt, black pepper, and ground cinnamon in a medium bowl. Let stand for 30 minutes. Refrigerate until chilled. Serve with crudités: sliced cucumbers, radishes, carrot sticks, etc.