Bring a large pot of water and 1 tablespoon salt boil to a boil. Add potatoes, turn heat to medium and cook until potatoes are soft when pierced with a fork, about 15 minutes. Make the sauce.
Trim stem end off tomatoes and make a "+" sign on the opposite/bottom of each. In a sauce pan, boil tomatoes in 3 cups of water for 10 minutes. Reserve 2 cups of cooking water. Peel tomatoes, transfer to a blender and add garlic, cumin, oregano, pepper, salt and one cup of cooking water. Puree until smooth.
In the same sauce pan heat oil over medium heat. Add sauce and let it cook for 1 minute. Add the remaining cooking water and simmer for about 5 minutes to reduce and thicken. Set aside.
Drain potatoes and transfer back into the pot. Add butter, remaining tablespoon salt, garlic, cumin, paprika and cheese. Mash the potatoes until everything is combined. Season to taste with salt if needed.
Wrap tortillas in 2 batches with paper towels. Heat in microwave for 10 seconds or on a hot skillet or griddle until soft and pliable to avoid cracking. Lay tortilla flat and fill half with heaping 2 tablespoons of mashed potatoes. Fold in half, pressing gently. Continue with remaining.
Meanwhile heat the oil in a frying pan until very hot (dip edge of tortilla in and if it sizzles, it's good to go).
Using tongs, carefully fry 4 tacos at a time for about 2 minutes or until tortilla looks golden and crunchy, turning to fry both sides. Remove tacos from the oil and place on a paper-towel lined plate. Continue with remaining tacos.