Heat a large skillet to medium heat and add the chorizo.
When the sausage begins to release some oil, add the diced onion to the skillet.
Cook the sausage and onion until the sauage begins to crisp a bit and the onion is nice and soft.
Remove the the sausage and onion from the pan and give it a quick wipe with a paper towel if there is too much oil in it.
Season the beaten egg generously with sea salt and fresh ground pepper, then add to the skillet stirring often until the eggs are almost set, but still a bit runny.
Add most of the manchego cheese to the eggs, but save a bit for garnishing the top of the tacos with.
finsh cooking the eggs, then divide them amongst the 4 tortillas. Top with the cooked chorizo and onion, then add a sprinkle of shredded manchego cheese.
Garnish with salsa and diced cilantro.
Notes
If you can't find manchego cheese, another hard cheese like parmesan or old white cheddar would be a suitable replacement.