Preheat the oven to 375°F (190°C). Grease a 9x13-inch baking dish with cooking spray or butter.

Roast the poblano peppers over an open flame or under a broiler until the skins are charred. Place them in a sealed plastic bag or cover with a towel for 10 minutes to steam, then peel off the skins. Remove the seeds and stems.

Layer half of the peeled poblano peppers in the bottom of the baking dish.

Sprinkle half of the shredded Monterey Jack cheese and half of the shredded cheddar cheese evenly over the peppers.

Add the remaining poblano peppers on top of the cheese layer, followed by the rest of the shredded cheeses.

In a mixing bowl, whisk together the eggs, flour, baking powder, garlic powder, cumin, salt, and black pepper until smooth. Gradually whisk in the milk until fully combined.

Pour the egg mixture evenly over the peppers and cheese in the baking dish.

Bake the casserole in the preheated oven for 30-35 minutes, or until the top is golden and the egg mixture is set.

Remove the casserole from the oven and let it cool for 5 minutes before slicing into squares.

Serve warm, optionally topped with tomato salsa for added flavor.