How to Make It
In a large nonstick skillet, heat 1 tablespoon of oil until shimmering. Add the chorizo and cook over high heat until crisp and lightly browned on both sides, 2 to 3 minutes. Transfer the chorizo to a plate. Add the onion, season with salt and pepper and cook over moderate heat, stirring frequently, until softened and lightly browned, about 5 minutes. Add the onion to the chorizo.
In a large bowl, beat the eggs with the flour, parsley, cilantro and scallion and season with salt and pepper. Fold in the chorizo and onion. Heat 1 more tablespoon of the oil in the skillet. Add the egg mixture, spreading out the chorizo and onion. Cook the tortilla over moderate heat until just set around the edge, about 2 minutes. Using a spatula, lift the edge of the tortilla and tilt the pan to allow the uncooked eggs to seep underneath. Continue cooking until the bottom is golden and the top is still a bit runny, about 5 minutes longer.
Set a large flat plate over the skillet and invert the tortilla onto the plate. Heat the remaining 1 tablespoon of oil in the skillet. Slide the tortilla into the skillet and cook over moderate heat until the bottom is set and browned, about 2 minutes longer. Slide the tortilla onto a plate, cut into wedges and serve warm or at room temperature.