Preheat oven to 350 degrees. Place chicken breast on baking sheet, drizzle with oil and season with salt and pepper. Roast in oven for 35 min. or until cooked through. Remove and let cool. Once cool enough to handle, shred chicken meat with a fork and set aside. (This can be done the day before.)
Turn oven temperature up to 400 degrees. Place pizza stone in oven to preheat for one hour for best results. Allow pizza dough to come to room temperature so it will be easier to work with.
For sauce, heat oil in medium saucepan over medium-high heat. Add garlic and saute until fragrant. Stir in tomato paste and cook for a minute to toast; this will add depth of flavor. Add tomato puree and Family Style Fajita Seasoning and bring mixture to a simmer. Cook for 10 min., stirring occasionally.
For veggies, heat oil in large saute pan over medium-high heat. Add peppers, garlic and onions and saute until onions are translucent, about 4 to 5 min. Season with salt and pepper. Remove from heat and set aside.
To assemble, roll pizza dough to a 13-inch diameter on a floured surface. Remove pizza stone from oven and carefuly place dough on top. Lightly cover the bottom of the pizza with the sauce. Sprinkle on chicken, sauteed veggies and cheese. Bake until crisp and golden, about 20 min.