Slice tofu into slabs about ½-inch thick. Heat olive oil in a large skillet. The skillet should be large enough to hold all the tofu in one layer. Heat oil on medium heat. Place tofu slices in the skillet and cover evenly with balsamic vinegar and soy sauce. Let it cook for a couple minutes, give the pan a shake. Sprinkle on the cilantro, cook another minute, and then flip each piece of tofu.
You should see the tofu has started to brown on the first side. Continue to sauté, shaking the pan periodically, until most of the liquid has evaporated. Turn the tofu again and add more browning to the first side. When is done, both sides should be browned, and full of flavor.
NOTES
I recommend using balsamic vinegar and soy sauce as base ingredients, but you can always substitute the balsamic with any vinegar, or citrus juice: lemon, lime, or orange juice. Lemon zest is nice too for a sour. Soy sauce can be replaced with Tamari, Braggs, or any kind of savory brown sauce you have. Worcestershire would probably work too.
Instead of the cilantro, you could use any fresh herb—such as basil, oregano, tarragon, thyme, parsley—or none at all. If you don’t have fresh herbs, you can try dried herbs of the same, or an herbs de Provence mix. A little black pepper, chili pepper, cayenne pepper, or jalapeño would add some spiciness, too, if you like.