Preheat oven to 425°. Brush a 17½x12½-inch rimmed baking sheet with oil. Place in oven until oil is very hot, about 8 minutes.
In a large bowl, whisk together cornmeal, flour, baking powder, 2 teaspoons salt, and garlic powder.
In a medium bowl, whisk together buttermilk, 6 tablespoons melted butter, eggs, green onion, and dill. Make a well in center of dry ingredients; add buttermilk mixture, stirring just until combined. Carefully spoon batter into hot baking sheet.
Bake until golden brown and a wooden pick inserted in center comes out clean, about 15 minutes. Let cool for 10 minutes. Remove from pan and cut into ½-inch cubes. Reserve 6 cups cornbread cubes. Save remaining cornbread cubes for another use. Place cubes on a parchment-lined baking sheet. Allow to sit, uncovered, until dry to the touch, about 2 hours or overnight.
Preheat oven to 375°.
Brush reserved 6 cups cornbread cubes with remaining 2 tablespoons butter and sprinkle with pepper and remaining ½ teaspoon salt. Bake until cornbread croutons are crisp and brown, about 15 minutes, stirring halfway through. Let cool completely.
Recipe by Taste of the South at https://tasteofthesouthmagazine.com/tomato-and-smashed-cucumber-salad/