Rinse and thoroughly wipe dry güero chiles with a paper towel.

Heat oil in a large cast iron skillet over medium heat. Add chiles and fry until char spots appear. Use metal tongs to turn each chile; about 12 minutes.  Transfer chiles to a large bowl. Set aside.

In the same cast iron skillet used to fry chiles, add onion slices. Cook over medium heat until soft and tender. Add onions to the bowl containing chiles.

Whisk together lime juice, soy sauce, Maggi Sauce and Tajin in a medium bowl. Add mixture to bowl with chiles and onion. Garnish with lime slices and a sprinkle of Tajin. Serve as a side to carne asada, cooked fish, tacos or roasted chicken.