Whisk together the flour, cornmeal, baking powder, baking soda, salt and 1 cup of the sugar in a large bowl. Whisk together the buttermilk, eggs and melted butter in a medium bowl. Add the wet ingredients to the dry ingredients and whisk to combine. Fold in the pears.
Transfer the batter to the prepared pan. ?Bake until a toothpick inserted in the ceanter comes out clean, 45-55 minutes. Cool in the pan for 15 min.; transfer to a wire rack.
Meanwhile, heat the rosemary, the remaining 1/3 c. sugar, and 1/4 c. water in a sm. pot over medium heat. Cook, stirring, until the sugar is melted. Remove from heat, cover, and let sit, stirring occasionally for 30 min. and up to 4 hrs. Discard the rosemary sprigs.
While the cake is still warm, brush the top and side with the rosemary syrup.
Serve warm or at room temperature with whipped cream, if desired.
TIP: Springform pans are slightly deeper than cake pans, giving this cake a heft that's worthy of a holiday meal. If you don't have a springform pan, butter and flour a 9 inch round cake pan and bake on a baking sheet (to catch any overflow).