In a saucepan over medium heat, sweat the onion in butter and salt until translucent.
In a large mixing bowl, place a paper bowl in the middle of the bowl. Resting the cob on the bowl in a vertical position remove only the tops of the kernel with a knife, using long smooth downward strokes and rotating the cob as you go. After the cob has been stripped, use the dull backside of your knife to scrape any remaining pulp and milk off the cob.
Add the corn and pulp mixture to the saucepan and cook over medium high until the juice from the corn has tightened. Add the rosemary. Sprinkle the corn with the sugar and turmeric. Stir constantly for about 2 minutes. Sprinkle the cornmeal onto the corn, using a whisk to combine well. Add the heavy cream and cook until the corn has softened, about 2 to 3 minutes. Remove the rosemary. Season with freshly ground black pepper.