Start with the onions. Heat olive oil with date syrup, stirring to avoid burning. Add thinly sliced onions whilst moving constantly on medium-high for a minute, add salt and reduce the heat to low. Cook for 10 minutes until some browning starts to appear, scraping the bottom of the pan if something sticks.
Deglaze the pan with coconut aminos and cook for 5-10 minutes more.
While the onions caramelize, cook pasta according to package instructions. Drain and return to the pot.
To a blender or hand mixer jug add 3/4 of the onions, 2 tbsp tahini and water. Blend until almost smooth, a few pieces of onions are fine.
Add the sauce and reserved caramelized onions to the pasta. Toss on low to coat and warm through. Serve with arugula on the side.