In a 10-inch cast-iron skillet, cook bacon over medium heat until crisp. Using a slotted spoon, remove bacon from skillet, and set aside. Add collards and sage; cook until collards wilt, approximately 1 minute. Remove from heat. Remove collard mixture from skillet, and set aside.
In a medium bowl, stir together cornmeal mix, pepper, buttermilk, eggs, and 1 tablespoon oil. Stir in collard mixture, bacon, and cheese. Add remaining 2 tablespoons oil to skillet; heat over medium-high heat until hot. Remove from heat. Pour cornmeal mixture into hot oil, smoothing top, if needed.
Bake until a wooden pick inserted in center comes out clean, approximately 20 minutes. Let cool in skillet on a wire rack 10 minutes.
Recipe by Southern Cast Iron at https://southerncastiron.com/smoky-southern-cornbread/