Heat the olive oil over medium high heat in a large stock pot. Add the onions and cook, stirring occasionally for five minutes until they are soft and translucent.
Add the apples, curry powder and cinnamon. Stir frequently so curry powder does not burn. (If it browns a little and sticks to the bottom of the pot, that is fine. This builds flavor that will blend into the broth when you add it.)
After a few minutes, when the curry spices smell delicious, add the vegetable or chicken broth to the pot. Bring to a boil, cover and then turn down the heat to medium or low and simmer for 15 to 20 minutes, or until apples are soft. Mix in squash puree and apple cider and heat until soup is hot, about 5 minutes. Puree the soup, either in a food processor or with an immersion blender. Add salt and pepper to taste. Add a little brown sugar if it isn’t sweet enough.
To make the cilantro lime yogurt, mix all ingredients in a bowl with a whisk or fork. Serve a dollop on each bowl of soup.
Note: Use any type of winter squash. Butternut is especially good and easy to find. Halve squash lengthwise and remove seeds and stringy parts. You can either steam the squash halves over hot water or bake them cut side down with a little water on cookie sheets until the squash is soft enough to be scooped out. You can also microwave the cut halves of squash until they are tender. Let cool, then scrape the flesh off the skin. Discard the skin and mash the flesh into a puree.