Cook ground beef in a large skillet over medium heat, stirring until meat crumbles and is no longer pink; drain and return to pan. Stir in chili powder and kidney beans.
Combine egg and ricotta in a small bowl; set aside.
Spread 2 tablespoons salsa in each of 2 lightly greased 9" x 5" loaf pans. Arrange 1 noodle over salsa in each pan. Spoon one-fourth ricotta mixture and one-fourth chili mixture over noodle in each pan; sprinkle each with 1/2 cup cheese. Spread 1/2 cup salsa over cheese in each pan. Repeat layers. Top each pan with another noodle, 1 cup salsa, covering noodle layer completely in each pan. Sprinkle each lasagna with remaining cheese. Cover tightly with aluminum foil, and refrigerate overnight. Bring to room temperature before baking.
Bake, covered, at 400° for 25 minutes; uncover and bake 5 more minutes or until lightly browned and bubbly. Let stand 10 minutes before serving. Serve with sour cream, if desired.