Preheat the oven to 425 (F) and prepare your pan by liberally spraying with cooking spray and lining with a piece of parchment paper; spray the parchment paper with cooking spray as well.
In a large bowl, combine 3 1/2 cups cornmeal, 1 3/4 cups flour, 1 3/4 tablespoons baking powder, and 2 1/2 teaspoons salt. Whisk until combined. Use a pint glass (or a bottle) to create a well in the center of the dry ingredients, and set aside.
In a large bowl, combine 1 3/8 cups granulated sugar, 2 1/4 cups whole milk, 5 eggs, and 1 1/4 cups melted butter. Whisk until thoroughly combined and the mixture is smooth — this'll take a surprisingly long amount of time because there is a LOT of the ingredients involved. Your arm will get tired, but persevere!
Once the mixture is smooth, pour the mixture into the well made by the dry ingredients (from the 2nd step). Use a rubber spatula to mix together, making sure to only mix until the ingredients are just combined. Again, this will take a long time because the batter is pretty thick and hearty, but you can do it! Once the ingredients are well combined and the batter is an even, thick yellow, transfer to your baking pan and bake in the preheated oven for 35 minutes, or until a skewer inserted into the center of the bread comes out clean. If the top of the cornbread browns too quickly, cover with aluminum foil. Let rest on a wire rack for 10 to 15 minutes, before serving immediately.