My grandma used to make these when I was a kid. They're very moist and very sweet. You can also add some coconut if you want to.
Preheat oven to 350 degrees F (175 degrees C). Grease muffin cups or line with paper muffin liners.
In a large bowl, cream together the butter and sugar until light and fluffy. Add the egg; beat well. Stir in the crushed pineapple and its juice. In a large mixing bowl, mix together the flour, salt, baking soda, baking powder and cinnamon. Add this mixture to the pineapple mixture; stir well. Scoop batter into prepared muffin cups.
Bake 350 degrees F (175 degrees C) for 20 minutes, or until a toothpick inserted into the center of a muffin comes out clean. Cool for 10 minutes in the pans before removing to a wire rack to cool completely.