Slowly cook the onions in 3 T of oil on medium-low heat until they are soft and brown, about 20 minutes.
Microwave the potatoes on high for 2 minutes to soften.
Heat the remaining 3 T of oil over medium-high heat. Cook the potatoes in batches so they are in a single layer, about 10 minutes each, or until they are slightly browned, flipping frequently. Sprinkle with salt and pepper.
Put slices of cheese on a tortilla and microwave for 20 seconds, or until cheese is melted. Top with 1/4 of the onions, potatoes, salsa, and ranch dressing. Add guacamole and/or sour cream if desired. Roll up into a burrito and enjoy. Repeat for other tortillas. But don't eat them all yourself; you'll die. A good death, but still death. Suit yourself. What do I know.