I use pickling cucumbers for this salad. As a substitute you may use European cucumbers or regular cucumbers with their seeds removed, if the seeds are tough. This is a perfect topping for vegan bibimbap.
3 pounds pickling cucumbers, peeled
1 medium-sized onion, peeled
1/2 teaspoon. salt
3 1/2 tablespoons lemon juice
About 1/4 to 1/2 teaspoon cayenne pepper
2 tablespoons crushed, roasted sesame seeds
2 teaspoons sesame oil (or just a few drops, to taste)
Cut the cucumbers and onion into very fine slices (a food processor may be used for this). Add the salt, lemon juice, cayenne pepper (Koreans like this dish very hot), sesame seeds, and sesame oil. Mix well, cover, and refrigerate. Serve cold or at room temperature.