Preheat the oven to 350°F (175°C). Place a rack in the center of the oven. Spray a 9 x 13-inch baking dish with nonstick cooking spray.

Prepare ingredients: thaw the 10 ounces frozen sweet corn and drain any excess liquid; shred the 3 cups sharp cheddar cheese; dice 3–4 large jalapeños (about ¾ cup). If you prefer less heat, remove the jalapeño seeds before dicing.

In a large bowl, whisk together the dry ingredients: 2 ½ cups all-purpose flour, 1 ½ cups yellow cornmeal, 1/3 cup granulated sugar, 2 tablespoons baking powder, 2 ½ teaspoons salt, and 1 ½ teaspoons garlic powder.

In a separate bowl or measuring cup, whisk together the wet ingredients: 2 cups buttermilk, 4 large eggs, and 1 cup unsalted butter (melted).

Pour the wet ingredients into the bowl with the dry ingredients and whisk until the batter is smooth and no large lumps remain.

Gently fold into the batter the thawed sweet corn, 2 cups of the shredded sharp cheddar cheese, and the diced jalapeños until evenly distributed. Do not overmix.

Transfer the batter to the prepared 9 x 13-inch baking dish and spread it into an even layer. Sprinkle the remaining 1 cup shredded cheddar cheese evenly over the top.

Bake in the preheated oven for 40–50 minutes, until the top is golden and the center no longer jiggles when you gently shake the pan. To confirm doneness, insert a toothpick into the center — it should come out clean or with a few moist crumbs (no wet batter).

Remove the cornbread from the oven and let it cool in the pan for about 10 minutes before slicing and serving.