Preheat the oven to 350°F (175°C). Prepare an 8x8-inch square baking dish or pan and place it on a baking sheet to catch any potential overflow during baking.

In a medium saucepan over medium heat, combine the chili and water. Simmer gently until the mixture is warmed through and slightly loosened in texture. If the chili appears too thick, add up to an additional 1/2 cup of water. Alternatively, microwave the mixture in 30-second intervals until heated evenly.

Remove from heat and pour the chili into the prepared baking dish, leaving approximately one inch of space at the top to allow for the cornbread topping.

In a medium mixing bowl, combine the corn muffin mix, egg, milk, kosher salt, and onion powder (if using). Stir until just combined and smooth; do not overmix.

Using a spoon, drop portions of the batter evenly over the chili. With the back of the spoon, gently spread the batter toward the edges of the pan until most of the chili is covered, allowing a few small areas to remain visible.

Place the baking dish (still on the baking sheet) in the preheated oven. Bake for 15 minutes, then rotate the pan and continue baking for another 15 to 25 minutes, or until the cornbread is risen and golden brown. A toothpick inserted into the center should come out clean.

Remove from the oven and allow the dish to cool for about 10 minutes before serving. This resting period allows the chili to set and makes it easier to portion neatly. Serve warm.