Set an oven rack in the upper third of the oven (about 6-inches from the heat) and set the oven on BROIL. Line a large rimmed baking sheet with aluminum foil.

Place the peppers on the prepared baking sheet and broil until the skins blister and blacken, about 5 minutes. Flip and continue to broil, an additional 5 to 6 minutes, until all sides are blistered and blackened.

Using kitchen tongs, transfer the peppers to a large bowl and cover with plastic wrap or aluminum foil. Let them rest, covered, for 15 minutes.

Then, use your hands to peel off and discard the charred skins. Remove the stems and gently break them in half to expose the seeds. Remove and discard the seeds from each half and set the halved poblanos aside.

Preheat oven to 350 degrees F with a rack set in the center position.

Meanwhile, in a large skillet, cook the ground beef with the onion over MEDIUM heat, breaking the beef up with a spoon until it’s crumbled and no longer pink.

Drain off the excess grease and return the skillet to the heat. Stir in the garlic, cumin, salt, pepper, and red pepper flakes, if using. Cook, stirring, for about 1 minute. Remove the skillet from the heat and set it aside.

In a large bowl, whisk the eggs with the milk. Add the flour and baking powder and whisk vigorously until mostly smooth. Set aside.

Coat a 9 x 13-inch baking dish with nonstick cooking spray.

Place half of the peppers in a single layer across the bottom of the dish (it’s fine if they overlap a bit).

Top with half of the meat mixture then layer with ¾ cup cheddar cheese and ¾ cup Monterey Jack cheese.

Spoon the remaining meat mixture over the top and place the remaining peppers over the meat in a single layer. Sprinkle the remaining cheese on top.

Slowly pour the egg mixture evenly over the ingredients.

Cover the dish with aluminum foil and bake for 30 minutes. Remove the foil and bake for an additional 14 to 16 minutes or until puffed and golden brown around the edges.

Remove from the oven and allow it to rest for 5 minutes. Garnish with cilantro, if desired. Slice and serve with sour cream, salsa, and/or hot sauce on the side.