Preheat the oven to 350°F.
Into a large, deep skillet over medium heat, add the olive oil. When the oil is hot, add the onion and cook for 3 minutes, until softened.
Add the pinto beans, black beans, refried beans, and taco seasoning. Continue cooking, gently mashing the refried beans and combining them with the pinto and black beans. Remove from heat and set aside.
In an 8x8-inch baking dish, layer 1 cup of crushed tortilla chips, 1/2 of the bean mixture and 1 cup cheddar cheese. Repeat with the remaining, chips, beans, and cheese.
Bake for 20 minutes, until cheese is melted.
Top with shredded lettuce, pico de gallo, and cilantro then serve warm.