How to Make It
In a large glass bowl, mix the rice vinegar with 1/3 cup of the sugar. Microwave at high power just until the sugar is dissolved, about 1 minute. Add the cucumber, toss to coat and refrigerate for 20 minutes, stirring occasionally. Drain, add the sesame seeds and keep chilled.
Meanwhile, light a grill. Set the pork loin fat side down on a work surface. Using a large, sharp knife, make a lengthwise slit down the length of the roast, leaving 1 1/2 inches of meat attached; open it like a book. Make a slit down the center of each lobe, and open up the loin to expose as much surface area as possible.
In a medium bowl, mix the soy sauce with the sambal oelek, garlic and the remaining 1 tablespoon of sugar. Add the pork, turn to coat and let stand for 5 minutes.
Remove the pork from the marinade, letting the excess drip off. Grill over moderate heat, turning once, until cooked through, about 12 minutes per side. Transfer the pork to a cutting board, cover with foil and let rest for 10 minutes. Slice the pork and serve with the cucumber salad.