To clean the nopales, carefully remove all the thorns and prickles with a knife and cut the edges of the nopal. (If you get clean nopales, skip this step)
Cut along the long side of each cactus, being careful not to reach the other side so it can open like a book.
In a pot, bring about two litres of water to boil and add the nopales with a tablespoon of salt and a tablespoon of baking soda, boil for 15 minutes and rinse thoroughly. Let it cool down.
For the salsa, char the tomatoes, onion and garlic in a skillet, turning them so that all sides are evenly darkened. Put all ingredients in a blender and blend until you get a smooth consistency.
Separate the egg whites from the yolk. Beat the whites until fluffy, and then slowly add the yolk whilst mixing.
Fill the nopales with cheese in the middle and pass them through the flour and the egg mixture.
Heat enough vegetable oil in a frying pan, fry the nopales for about two minutes bathing the part that remains upwards with the help of a spoon before turning and then leaving for another 2 minutes or until it is golden brown.
Serve on a plate and bathe them with the salsa.
¡Buen provecho!