Step 1: Preheat your oven to 400F (200C). Cut the butternut squash in half lengthwise, remove the seeds, and place cut-side down on a baking sheet.
Step 2: Roast the squash for 45-50 minutes or until the flesh is very tender. Let it cool, then scoop out the flesh and blend until smooth to create a puree.
Step 3: Reduce the oven temperature to 350F (175C) and grease a 9-inch cake pan or loaf tin.
Step 4: In a large bowl, cream together the softened butter and dark brown sugar until the mixture is light and fluffy.
Step 5: Add the eggs one at a time, beating well after each addition, then stir in the vanilla extract and 1.5 cups of the prepared roasted butternut squash puree.
Step 6: In a separate bowl, whisk together the flour, baking soda, baking powder, cinnamon, nutmeg, ginger, and salt.
Step 7: Gradually fold the dry ingredients into the wet ingredients until just combined, being careful not to over-mix the batter.
Step 8: Pour the batter into the prepared pan and bake for 35-40 minutes, or until a toothpick inserted into the center comes out clean.
Step 9: Allow the cake to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.