Heat olive oil in medium skillet over medium heat and cook onion and taco seasoning mix, stirring occasionally, until onion is tender, about 4 minutes. Stir in refried beans; heat through.
Process bean mixture in blender until smooth. Spread onto bottom of 2-qt. (2-L) glass baking dish; set aside.
Process avocado, Hellmann's® Real Mayonnaise, red chile pepper and lemon juice in blender or food processor until smooth. Spread over bean layer. Sprinkle with red onion, then add tomatoes; set aside.