Butter an 8-inch square baking dish, and place it in the hot oven while you prepare the batter.
Sift or stir together the flour, cornmeal, baking powder and baking soda.
In a mixing bowl, beat the eggs and the melted butter until well-blended. Add the sugar, salt, milk and vinegar and beat well. Stir the dry ingredients into the egg mixture just until the batter is smooth.
Pour the batter into the heated dish. Pour the heavy cream into the center of the batter. Do not stir. Check the cornbread after 45 minutes. It is done when the top becomes lightly browned.