1Heat oven 375. Spray 13x9 inch pan with cooking spray, In 10 inch skillet, cook beef and chili powder over medium-high heat 6 to 8 minutes, stirring occasinally, until throughly cooked; drain. set aside.
In small bowl, mix sour cream, mayonnaise, cheese and onion; set aside.
In medium bowl, stir Bisquick mix and cold water with fork until soft dough forms. Using fingers dipped in bisquick mix. press dough in bottom and 1/2 inch up sides of pan. Layer beef, tomatoes and bell pepper on dough. Spoon sour cream mixture over top; spread evenly over vegetables to cover.
Bake uncovered 25 to 30 minutes or until edges are light brown.
For a chicken version of this Mexican bake, use 2 cups diced cooked chicken in place of the ground beef.