In a Ziplock bag, mix the garlic powder and cumin together; add the cubed potatoes, seal the Ziplock, and toss it all together until potatoes are coated evenly.
In a large, heavy skillet over medium heat melt the oil and butter together.
Add the seasoned potatoes and cook, stirring frequently, until they're a nice, golden brown, about 10 minutes; cover and cook an additional 10 minutes or until potatoes are tender then season to taste with salt and pepper.
Transfer the sautéed potatoes to a non-stick baking sheet and bake at 475 degrees F for 10 minutes, stirring occasionally, until potatoes are nice and crisp.
When potatoes are almost done baking, place the cubed Velveeta, salsa, and Tabasco into a microwave-safe bowl (I use a large Pyrex measuring bowl) and microwave for 1 minute; stir and microwave another minute; stir again and microwave for 1 more minute, then stir until smooth.
For each serving, place some potatoes in a bowl, then pour over 1/4 of the melted Velveeta cheese sauce, top with some sour cream, then sprinkle with chopped green onion.