1For the Caramel Sauce, melt butter in medium saucepan on medium heat. Add sugar; cook and stir with wire whisk 6 to 7 minutes or until mixture turns a deep amber color. Carefully stir in cream, vanilla, ground guajillo chile and sea salt. (Mixture will be bubbly.) Whisking constantly, cook 1 to 2 minutes until sauce thickens and coats back of spoon. Let stand 5 minutes or until slightly thickened.
2Preheat oven to 325°F. For the Bars, mix flour, ground guajillo chile, baking soda and salt in medium bowl. Set aside. Mix butter and sugars in large bowl until well blended. Add eggs and vanilla; mix well. Add flour mixture; mix just until moistened. Stir in chocolate chunks. Reserve 1 cup of the batter. Spread remaining batter in foil-lined 13x9-inch baking pan sprayed with no stick cooking spray. Bake 15 minutes.
3Pour Caramel Sauce over baked layer in pan, spreading to within 1/2 inch of edges. Drop reserved 1 cup batter by spoonfuls over caramel layer. Cut through batter with knife several times for a marble effect.
4Bake 15 to 20 minutes longer or until top is golden brown and center is set. Cool in pan on wire rack. Use foil handles to remove dessert from pan. Place on cutting board and cut into bars.