Press out, bake and pinch the sopes. Heat a griddle or very large (12-inch) heavy skillet over medium heat. Adjust the consistency of the masa, if necessary, working in a little water to create a dough that is soft—it should be tacky but not sticky. Mix in the salt. Divide into 8 balls, each weighing 2 ounces. Using a tortilla press lined with two pieces of plastic, gently press a ball of masa between the sheets of plastic into a disk that is 3 ½ inches in diameter, about ¼ inch thick. Peel off the top piece of plastic, flip the uncovered disk onto one palm and peel off the second piece of plastic. Lay this fat little tortilla onto the hot griddle and bake until lightly browned underneath, about 3 minutes, then flip over and bake the other side. Remove from the heat (it is called a gordita at this point) and let cool just until handleable (don’t let the gordita cool completely or the malleable masa will become firm). With thumbs and forefingers of both hands, pinch a shallow border all around, then pinch up little “waves” all over the bottom (now you call it a sope. Once you get into the rhythm of the process, you’ll quickly move through the baking and pinching of all the sopes. This can be done an hour or so ahead, but, for that perfect texture, the fresher, the better.
Finish the sopes. If your griddle has edges, you can use it to shallow fry the sopes; if not, change to a very large skillet. Heat the griddle or skillet over medium. Film the surface liberally with oil (enough to allow the sopes to lightly fry) and, when hot, lay on a few sopes in an uncrowded layer. Drizzle a little oil over the top of each one. (The typical street vendor set up allows them to splash a little hot oil over each one.) In a minute or 2, the sopes will be crisp underneath. Splash on a little salsa, then sprinkle on some cheese and the onion-cilantro mix. Serve without hesitation.
For the professional: This is an average- to small-size sope, so feel free to shrink or expand them. Unless you can bake and pinch the sopes just before service and have a dedicated griddle space to finish them, these can be hard to work into a regular restaurant flow. Easier are the deep-fried sopes, which are much more forgiving, both before and after they are fried. On a buffet or in banquet service, these sopes always suffer in my opinion.