Adapted from Bon Appetit via Tea Cup Tea
- ¾ C plus 2 Tbsp. unsalted butter
- 2 medium onions, thinly sliced
- 1 tsp kosher salt plus more
- Freshly ground black pepper
- 3 medium apples, thinly sliced
- 4 Tbsp sugar, divided
- 3 tsp fresh thyme leaves, divided
- 1½ C cornmeal
- 1 C all-purpose flour
- 1 Tbsp baking powder
- 2 large eggs
- 1½ C buttermilk
Preheat oven to 400°. Melt butter in a cast-iron or other heavy skillet over medium-high heat. Pour all but 2 Tbsp. butter into a small bowl; set aside.
Add onion to butter in skillet, season with salt and pepper, and cook, stirring occasionally, until onion is softened and beginning to brown, about 4 minutes. Add apples, 2 Tbsp. sugar, and 2 tsp. thyme and cook, stirring often, until apples are softened, about 4 minutes. Transfer onion mixture to a medium bowl and reserve skillet.
Whisk cornmeal, flour, baking powder, 1 tsp. salt, and remaining 2 Tbsp. sugar in a large bowl. Gradually whisk in eggs, buttermilk, and ¾ cup reserved melted butter until smooth (no lumps should remain). Fold in half of onion mixture and scrape batter into reserved skillet. Top with remaining onion mixture and remaining 1 tsp. thyme.
Bake cornbread until golden brown and a tester inserted into the center comes out clean, 30–40 minutes.