Steps

1. Add 1.5L water and 1.5 tbsp salt to a pot and heat over low heat. [This is the key!] Since it will be rinsed, we use a saltier water than usual to account for salt loss during washing.
   🕒 00:18
2. Rub 1 cucumber with salt after slightly moistening it to remove any raw smell.
   🕒 00:41
3. After rubbing the cucumber well, rinse it with water once your hands turn green.
   🕒 00:55
4. Place a slicer over a bowl, and once the cucumber is wiped dry, slice it after cutting off the ends.
   🕒 01:06
5. Core the base of 1/2 onion and slice it.
   🕒 01:37
6. Add 2 pinches of salt and 2 pinches of sugar to the sliced onion, and firmly massage it to remove excess moisture. [This is the key!] Massaging with salt draws out the vegetable's moisture, helping it blend better with the dressing and preventing it from becoming watery. Adding sugar also helps with osmosis, allowing the salt to penetrate without leaving a salty taste.
   🕒 01:56
7. Once the onion has softened, turn up the heat of the pot where the pasta is cooking to a boil.
   🕒 02:37
8. Once boiling, add 200g spaghetti, broken in half, to the pot and cook for 2 minutes longer than the package instructions. [This is the key!] Slightly softer pasta is delicious for salad pasta. There's no worry about the noodles getting mushy since they will be chilled in cold water.
   🕒 02:45
9. In a large bowl, combine 4 tbsp mayonnaise, 2 tsp Worcestershire sauce, 2 tsp lemon juice, 10g Parmesan cheese, 4g mustard paste, and 1 pinch MSG (Umami Seasoning).
   🕒 03:17
10. Add 1 can of tuna to the bowl and mix thoroughly until it forms a thick, cohesive sauce. [This is the key!] Mix well to integrate the tuna's oil and dressing, preventing separation and ensuring the sauce clings well to the pasta.
    🕒 03:55
11. Squeeze the water out of the salt-massaged cucumber and onion with paper towels, then add them to the sauce bowl.
    🕒 04:28
12. Mix thoroughly to ensure the vegetables and sauce are well combined.
    🕒 04:43
13. Quickly rinse the cooked spaghetti under cold running water and drain well. [This is the key!] Thoroughly chilling the pasta prevents it from becoming mushy and stops the mayonnaise from separating.
    🕒 05:01
14. Pat the surface of the drained pasta dry with paper towels, then add it to the bowl with the sauce and vegetables.
    🕒 05:38
15. Mix thoroughly to coat the pasta, sauce, and vegetables evenly.
    🕒 05:53
16. Transfer to a serving dish and generously top with leafy greens (baby leaves, green leaf lettuce, sunny lettuce, etc.).
    🕒 06:36
17. Garnish with black pepper and parsley to taste, and it's ready. Enjoy!
    🕒 06:57