Start by grating the onion and transfer it to a bowl, add the ground beef, parsley to taste and season with black pepper and chimichurri, mix very well so that the spices can be absorbed into the meat.
Then whisk the eggs very well.
Spread butter all over a skillet, greasing very well.
Place a tortilla dough in the skillet and cover it with the meat, spread evenly.
Grate the mozzarella cheese and spread half of it all over the meat, add the other tortilla dough and spread the beaten eggs all over it.
Take skillet over medium-low heat, close it, and let it all cook for about 10 minutes.
Cut the tomato into thin slices and set aside.
After the indicated cooking time, flip the tortilla and cover it with the tomato slices, season with salt to taste, also add the other half of the cheese, close the skillet again and let the cheese fully melt.
Top with parsley to taste.
Serve.