Gather all ingredients. Preheat the oven to 350 degrees F (175 degrees C). Grease a 9x13-inch baking dish with cooking spray.
Evenly layer poblano peppers from 1 can in the bottom of the prepared baking dish.
Sprinkle with ½ of the Jack and Cheddar cheeses, then cover with remaining poblano peppers.
Mix eggs, evaporated milk, and flour together in a bowl; add ½ cup milk to thin to desired consistency. Pour over chiles.
Bake in the preheated oven for 25 minutes. Pour tomato sauce evenly over the top; continue baking for 15 more minutes.
Turn broiler on. Sprinkle top with remaining Jack and Cheddar cheeses. Place under the broiler until cheese is melted, 2 to 3 minutes. Serve and enjoy!
