Roast the peppers: Line a large baking sheet with aluminum foil and place poblano peppers on top. Set your oven rack directly underneath the broiler and turn the broiler on.

Broil poblanos for 5 minutes, or until the skin is blackened and blistered. Carefully flip them over and broil for another 5 minutes, or until the skin is blackened and blistered.

Remove them from the oven and loosely cover the baking sheet with aluminum foil or plastic wrap to keep in some of the heat and help them steam. Let them sit for 5 minutes.

Peel the peppers: Peel and rub off as much of the loose skin on the peppers as possible. It doesn't have to be perfect, just as much as you can.

Cut a small slit down the middle of the peppers with a knife. (If you don't want the peppers too spicy, you can remove some of the seeds.)

Stuff the peppers: Carefully stuff the peppers with the cheese. Some of the peppers will be extra fragile because of the roasting process and may tear – that's okay.

Gently close the opening of the peppers and secure it shut with 1-3 toothpicks. Use as many as you need to ensure that the cheese won't ooze out during the frying process. Set aside.

Prepare for frying: Heat the frying oil in a large saucepan or deep skillet over medium-high heat. Line a baking sheet with paper towels and set aside. While oil is heating up, prepare the batter.

Make the batter: Separate the egg whites from the yolks into two separate bowls. Using an electric hand mixer, beat the egg whites until stiff peaks form.

While continuing to beat the egg whites on low, add in the egg yolks one at a time until all of them are fully mixed in. The batter should be light, fluffy, and smooth.

Coat the peppers with batter: Place the flour and salt into a separate shallow bowl or plate. Gently roll the stuffed peppers in the flour mixture, then dip them in the egg batter and gently place them in the hot frying oil.

Fry the chile rellenos: Fry the peppers for 3-5 minutes per side, until the batter is golden brown and crispy. Transfer the peppers to the lined baking sheet to drain off any excess oil.

Serve: Immediately serve chile rellenos on a plate with some salsa, freshly chopped cilantro, and some cotija cheese. (Don't forget to remove the toothpicks when you first cut into the peppers!)

Add tomatoes, onion, garlic, jalapeño, cilantro, and salt to a blender. Puree until smooth.

Heat olive oil in a small saucepan over medium-high heat. Add blended salsa and bring to a boil.

Reduce heat to low and simmer, stirring occasionally for 8 minutes. Remove from heat, taste and season with more salt if desired.