Boil the spaghetti noodles.
Rinse the noodles under cold water and drain well.
Thinly slice the onion, cucumber, and cherry tomatoes.
Mix soy sauce, olive oil, lemon juice, and garlic to make the sauce.
In a large bowl, combine the cooked noodles, vegetables, and sauce, and toss well.
Transfer to a dish and sprinkle with sesame seeds.