In a large cast iron skillet or oven-safe skillet, heat oil over medium-high heat. Add the onions, bell pepper, and garlic, and cook, for about 4 minutes until veggies have softened.
Add in the ground turkey, chili powder, cumin, ½ teaspoon salt and pepper, with a wooden spatula break up the ground turkey and stir with the vegetables as it cooks, for about 5 minutes. Add in the tomatoes and corn, and stir to combine.
In a medium bowl, combine the cornmeal and water. Pour the cornmeal mixture into the skillet and stir to combine with the meat and veggies. Reduce to the to simmer.
Make the cornmeal topping:
In a medium saucepan over medium heat, combine the milk, butter and remaining ½ teaspoon of salt. Stir frequently until it comes to a simmer -do not boil it. Slowly add in ½ cup cornmeal and cook, stirring, until it has thickened but isn't quite stiff. Remove the pan from the heat.
With the pan away from the heat, add in the cheese and whisked eggs.
Spread the topping over the skillet and spread to cover.
Bake:
Place the skillet into the preheated oven and bake for 20 minutes until the cheese is golden brown and the cornmeal mixture is cooked.
Remove from the oven and let it rest for 10 minutes.
Serve with chopped cilantro and avocado.
Notes
If you don't have a large oven-safe skillet or pan, cook the meat and veggies in any large pan. Transfer everything into a greased, 9x13 baking dish. Spread the cornmeal topping and bake as directed.