Preheat oven to 375°F (190°C). Grease muffin tin or line with paper liners.
In a large bowl, cream together the butter and sugar until light and fluffy.
Add the eggs one at a time, beating well after each addition.
Add the squash and mix until well blended.
In a separate bowl, sift together the flour, baking soda, baking powder, salt, cinnamon, nutmeg, and cayenne pepper. Add to the squash mixture and mix until just blended.
Gently fold in the raisins if using.
Spoon the batter into the prepared muffin tin, filling each cup about two-thirds full.
Bake for 20-25 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Let cool in pan for 10 minutes before transferring to a wire rack to cool completely.
Interesting Facts
Squash is a member of the Cucurbitaceae family, which also includes cucumbers and melons.
Squash is a good source of vitamins A and C, potassium, and dietary fiber.
Muffins are believed to have originated in the United States in the early 19th century.
Muffins are a popular snack food in the United States.