Check items off while grocery shopping - it’s remembered here.
Julienne the cucumber with a mandoline, place in a mixing bowl, and sprinkle with salt. Let sit 10 minutes, then press with your hands to squeeze out the water.
Make the dressing: mix 2T black sesame, 2T perilla oil, 2T tsuyu, and 0.5T soy sauce together well.
Slice a little tomato and set aside.
Boil the buckwheat noodles, adding a splash of cold water to the pot about three times, then rinse in cold water.
Plate the noodles, top with the cucumber from step 1 and the tomato from step 3, and pour over the dressing from step 2.