Bring a large pot of salted water to a rolling boil. Cook the spaghetti until al dente according to package directions. Reserve about ½ cup of pasta water before draining. Set pasta aside.

Thinly slice the onions using a mandoline. Add to a large pan over medium-low heat with a drizzle of oil. Cook slowly, stirring occasionally, until golden, soft, and jammy, about 20-25 minutes. Add the brown sugar midway through to deepen the caramelization.

Add AP seasoning, Italian seasoning, smoked paprika, and chicken bouillon to the caramelized onions. Cook for 30 seconds until fragrant. Stir in the Worcestershire sauce, soy sauce, and chili oil.

Pour in the reserved pasta water and heavy cream. Simmer and reduce slightly. Add the grated Parmesan cheese and stir until the sauce is smooth and glossy. Add the pasta to the pan and toss until every strand is coated.

Season the salmon fillet and cook in a hot pan until crispy on the outside and tender in the middle. Glaze with Japanese BBQ sauce during the last minute of cooking for a sticky, caramelized finish.

Plate the pasta, lay the glazed salmon on top, and finish with extra Parmesan, fresh parsley, and a crack of black pepper. Serve immediately.