Preheat oven to 400F and grease a 1.3 quart baking dish (either 8x8 inch or 12x5 inch, see notes).
In a large bowl, mix together the cornmeal, flour, baking powder, sugar, baking soda, salt, and nutmeg. Add the buttermilk, eggs, and olive oil and stir until almost combined. Add the diced sage, corn kernels, and shredded cheddar cheese.
Pour the batter into the greased baking dish and bake at 400F for 35-40 minutes, or until a toothpick inserted into the center comes out clean. If the edges are starting to brown but the center is still uncooked, turn the heat down to 350F after 35 minutes and continue to bake until a toothpick inserted into the center comes out clean. Remove from heat and allow to cool slightly before serving.