Prepare the ingredients: dice the onions. Peel and mince/press the garlic. Peel, seed, and dice the butternut squash into almond-size pieces. Peel and dice the sweet potato, also into almond-size pieces. You can chop the squash and potato into larger pieces if you want, but it will increase the simmer time in Step 5.
Saute the olive oil, onion, and garlic in a large pot over medium heat for 4-8 minutes, until the onion is softened. While the onion is softening, rinse the red lentils (or drain and rinse the chickpeas, if using those instead of lentils)
Add the squash and sweet potato and stir to combine. Add a pinch of salt and continue stirring for 1-2 minutes.
Add the vegetable broth, diced tomatoes (with juices), coconut milk, red lentils, tomato paste, turmeric, ground cumin, curry powder, chili powder, salt, and black pepper. Stir well to combine.
Increase heat and bring to a boil. Reduce the heat to medium, stir again, and simmer uncovered for about an hour, stirring occasionally, until the squash and potato are easily stabbed through with a fork and are starting to dissolve. Reduce the heat when the bottom of the pot starts to burn.
While the stew is simmering, stem and coarsely chop the chard.
After the squash and potato are done cooking, add the apple cider vinegar. Taste and adjust the other seasonings (eg. salt, black pepper, curry powder, chili powder) if desired.
Stir in the chard, and cook for another couple minutes until the leaves are wilted.