Put all the dressing ingredients except the sesame seeds in a blender. Blend until smooth - reserve 1/4 cup of dressing in a container to use for marinade. Add sesame seeds to the remainder of the dressing and stir.
Slice the pork loin into thin slices (1/4") and place in a bowl. Pour part of the marinade over the slices and coat completely. Let sit for at least 10 minutes.
Pour the oils into a wok or a large skillet. Make sure to spread the oil to cover the surface of the pan. Heat to medium-high temperature. Add the pork slices and cook thoroughly and slightly browned.
For the pickled onions - combine the water, vinegar, and sugar in a saucepan and simmer on the stovetop until the sugar has dissolved. In the meantime, slice the onion into desired sizes. Once the liquid is heated through and the sugar is dissolved, pour the liquid over the onions and let sit for at least 15 minutes. Drain before serving.
Assemble bowls using the lettuce and/or rice as the base. Add the pork and any preferred toppings. Enjoy!