Peel butternut squash and chop into cubes. You can also roast the butternut squash first by slicing it in half, brushing the inside with a little olive oil and cooking in the oven at 375°F/190°C for about 1 hour. Either way works.
Heat oil in a large pot under medium heat. Place chopped onions in the oil and stir. Add the chopped garlic and then the spices. Allow the onions to cook for a few minutes whole stirring occasionally.
Add the chopped tomato and stir, then add the butternut squash. Pour the vegetable broth over the vegetables, then add the lentils. Bring to a boil, then turn to low and let simmer for about 30 min-1 hour until the lentils are cooked through and the butternut squash is soft.
Once every thing is cooked well, turn off the heat. This is where a hand blender like this one comes really in handy and makes clean-up really easy. Of course, if you don't have a hand blender your an use a regular blender, but make sure you wait for the soup to cool a little bit first. Blend the soup until it is pureed well, then add salt and pepper to taste.