Preheat the BROILER on low and roast the poblano for 5-6 minutes until the skin has blackened. Immediately remove the pepper from the oven and put inside a food safe airtight bag to cool. This method allows the steam to naturally loosen the blackened skin of the pepper. Once the pepper is completely cooled, peel the skin from the poblano, remove the seeds and stem and dice.
Preheat the oven to BAKE at 400 degrees.
Core and dice the tomatoes and spread on a parchment paper lined sheet pan. Add the minced garlic and shallot to the sheet pan and drizzle with olive oil, 1/2 teaspoon of salt and fresh cracked pepper. Roast the tomatoes in the preheated oven for 15-18 minutes until softened.
Cook the spaghetti according to the package instructions.
Meanwhile, in a 9x13 pan add the sour cream and 1 cup of shredded cheese and season with smoked paprika, cumin and cayenne pepper.
Once the pasta is cooked, drain off the water and add the hot pasta directly into the 9x13. Toss the pasta in the sour cream mixture until combined.
When the tomatoes, onion and garlic have finished roasting, add them to the casserole dish along with the pulled chicken and raw diced bell pepper. Carefully mix everything together and taste for salt and pepper.
Once you feel the spaghetti is seasoned well, lower the temperature of the oven to 350 degrees, top the 9x13 with the remaining cup of cheese, and bake the casserole for 25-30 minutes until everything is hot and bubbly.
Let the chicken spaghetti cool for about 10 minutes before serving and top with cilantro if using.