Preheat your broiler and place the rack about 6 inches from the heat source. Line a baking sheet with foil and place the whole poblano peppers on top.

Broil for 10–15 minutes, turning occasionally with tongs, until the skins are blistered and blackened.

Transfer roasted peppers to a plastic bag or a bowl covered with plastic wrap. Let them steam for 10 minutes to loosen the skins. Then peel off the skins, cut off stems, open the peppers, and remove seeds. Set aside.

Preheat the oven to 350°F (175°C). Lightly grease a 3-quart baking dish with nonstick spray.

Lay half the roasted poblano peppers in a single layer on the bottom of the dish.

Sprinkle 1 cup of Monterey Jack and ½ cup of cheddar cheese over the peppers.

Repeat with another layer of peppers and the remaining cheese.

In a medium mixing bowl, whisk together the eggs, milk, flour, baking powder, onion powder, garlic powder, salt, and black pepper until fully combined and smooth (no lumps of flour).

Pour the egg mixture evenly over the layered peppers and cheese.

Place in the preheated oven and bake for 45 minutes, or until the center is puffed and set, and the top is golden around the edges.

Let the casserole cool for 5–10 minutes before slicing.