Boil the tomatoes and serrano peppers, then blend them with the garlic clove. In the skillet where you'll cook the sauce, sauté some onion slices, then add the blended sauce and salt to taste.

For the filling, finely chop some onion and mix it with the cheese.

To serve, lightly fry the tortillas in oil, then dip them in the sauce. Fill each tortilla with the cheese and onion mixture.

Finally, roll them up and top with more cheese and sour cream.