Cut potatoes in half and place in a large bowl. Add olive oil, salt and cumin. Toss to coat all sides. Line a baking sheet with foil. Place the potatoes on the foil, cut side down. Bake in a 400-degree oven for 25 minutes, until tender. Allow to cool.
While they are baking, remove the casing from two chorizo links. Brown in a skillet. Add the onion and sauté until tender. Allow to cool.
Then chop in a food processor, so the sausage has a finer consistency.
Once the potatoes have cooled, scoop out the potato using a small spoon. Be sure to leave a rim, so the sides don’t cave in.
Place the potato meat into a large bowl and mash. Add the cooled chorizo. It will be a meatball consistency. Press the filling back into the potato shells. (You can freeze these at this point. If you do that, allow them to thaw. Then, reheat the potatoes in a 400 degree oven for 10 minutes before continuing on with the next step).
Top each potato with a slice of cheese. Place under a broiler for 2-3 minutes, or until cheese melts. Drizzle with tomato sour cream aioli (recipe below) and garnish with diced tomatoes.