
Bring a large pot of salted water to a boil. Cook the pasta until just al dente, then drain, rinse briefly under cool water, and set aside so it does not overcook.



Heat 1/4 cup oil in a large skillet over medium-high heat. Add the chopped tomatoes, spinach or waterleaf, chili peppers, red chili, habanero, garlic, and turmeric. Cook, stirring often, until the tomatoes break down, thicken, and darken into a concentrated sauce.



Stir in the soy sauce, fish sauce, lemon juice, and 1 tablespoon brown sugar. Simmer for 3 to 5 minutes, then taste and add the remaining brown sugar if you want a sweeter balance. If the dressing looks too thick or dry, stir in a little more oil until it has the texture of a thick vinaigrette.



Remove the dressing from the heat and let it cool completely. For the best texture and flavor, chill it in the refrigerator until cold before tossing with the pasta.



Add the cucumber, red onion, and chopped peanuts to the cooled pasta. Pour over the cold tomato-chili dressing and toss until everything is evenly coated. Serve chilled or at cool room temperature.




