Preheat the oven to 400°F. Grease a 9 x 13-inch baking pan with nonstick cooking spray.
In a large nonstick skillet, heat the 2 tablespoons oil. Add the chicken and season with the garlic powder, Italian herbs and salt and pepper to taste. Cook the chicken until cooked through, about 5 minutes. Remove the chicken from the pan.
Add the 2 tablespoons flour to the drippings in the pan and stir well to combine. Over low heat, cook the roux until bubbly. Slowly whisk in the milk and cook until thickened. Season the white sauce with salt and pepper to taste.
In a large bowl, whisk together the 2 cups flour, the baking powder, and the ONE teaspoon salt. Add the olive oil and the buttermilk, stirring gently until just combined. Pat this mixture into the bottom of the prepared pan.
Chop the chicken into bite-sized pieces.
Spread the white sauce over the biscuit dough. Sprinkle the chopped chicken, chopped tomatoes, and red onion to taste. Sprinkle the cheese over all.
Bake the pizza for 12 to 15 minutes. The crust will be cooked through and the toppings will be golden. Sprinkle the chopped basil over the top before slicing and serving.
Leftovers can be stored in the fridge for up to 4 days.