01 - Arrange eggs in a saucepan and cover with cold water. Heat over medium-high until boiling, then cover, remove from heat, and let eggs stand for 10 minutes.
02 - Drain eggs and cool under cold running water. Peel carefully once cooled.
03 - Slice eggs lengthwise and remove yolks. Set egg whites aside on a serving platter.
04 - Mash yolks in a mixing bowl with mayonnaise, Dijon mustard, Tajín seasoning, lime juice, cilantro, and red onion until a smooth mixture forms. Season with salt and black pepper.
05 - Spoon or pipe the filling evenly into the egg white halves.
06 - Dust with extra Tajín and garnish each half with cilantro leaves and lime wedges if using.
07 - Refrigerate until chilled and serve cold.