Slice the chicken breast into 1-inch cubes and place in a large mixing bowl.
Toss the chicken with 2 tsp salt, spicy Italian seasoning, dried parsley, garlic granules, smoked paprika, and olive oil until evenly coated.
Preheat your oven to 380°F (190°C).
In a large oven-safe dish, combine the thinly sliced red and white onions with the chopped sun-dried tomatoes, 1 tsp salt, Italian seasoning, and 2 tsp paprika.
Slice the very top off the garlic bulb to expose the cloves and nestle it into the center of the onion mixture.
Spray the onion mixture and garlic bulb with avocado oil spray, then cover the dish tightly with foil and bake for 45 minutes.
While the onions roast, cook the linguine in a large pot of boiling salted water until al dente, reserving 0.5 cup of pasta water before draining.
Remove the onion dish from the oven and carefully squeeze the softened roasted garlic cloves out of their skins directly into the dish.
Mash the garlic with a fork and stir in the light evaporated milk, light cream cheese, parmesan, and soy sauce until the cheese is melted and the sauce is smooth.
Increase the oven temperature to 400°F (200°C) and spread the seasoned chicken cubes onto a parchment-lined sheet pan.
Bake the chicken for 18 minutes, then turn on the broiler for an additional 3 to 5 minutes until the edges are golden and crisp.
Gently fold the cooked linguine and fresh parsley into the creamy onion sauce, adding a splash of reserved pasta water if needed to reach a silky consistency.
Serve the indulgent pasta in bowls topped with a generous portion of the herb-roasted chicken.