In a large skillet heat 1 Tbsp. olive oil or bacon fat over medium-high heat. Add the chopped onion and cook until softened. Move to side of pan and add broken-up bits of chorizo into the pan. Stir until sausage is cooked through but not necessarily browned. If not using LEAN choriza, drain the excess fat from the pan before proceeding.
Crack the eggs one at a time into the pan. Break the yolks and stir the eggs into the sausage. Add a light sprinkling of salt. Stir constantly until the eggs begin to set, but are still moist. Remove from heat.
Serve immediately with a side of warmed corn tortillas and cilantro as a garnish, if desired.