Cook the bucatini in a large pot of salted boiling water until al dente. Reserve 1/2 cup of the pasta water, then drain.
Meanwhile, melt the dairy free butter in a large skillet over medium heat. Add the garlic and cook for 1 minute until fragrant.
Stir in the gochujang and tomato paste and fry for 2 minutes, stirring constantly, until it darkens slightly and smells toasty.
Whisk in the coconut milk, nutritional yeast, soy sauce and honey. Simmer for 2 to 3 minutes until smooth, glossy and slightly thickened.
Add the pasta and a splash of the pasta water and toss until the creamy sauce coats every strand, adding more water if needed. Turn off the heat and drizzle with sesame oil.
Serve topped with green onions and toasted sesame seeds.