Preheat oven to 350 degrees. Spray an 8 by 8 pan. In a sauce pan mix the tomatoes and broth. Heat to boiling. Mix flour into sour cream and add hot tomato liquid to sour cream 1/4 cup at a time, mixing well before each addition. when you have doubled the volume of the sour cream with tomato sauce, pour mixture into pan with remaining hot tomatoes. Mix thoroughly and cook until thickened. Pour 1/2 cup into bottom of 8 by 8 pan. Layer half of tortilla pieces onto sauce, then layer half of chicken on top. pour other half of sauce over, layer remaining tortilla pieces, and remaining chicken. Top with cheese and cover with foil. Bake for 20 minutes or until hot and bubbly.