Heat oven to 400°F. In 12-inch skillet, cook beef and onion over medium-high heat, stirring frequently, until beef is thoroughly cooked; drain. Stir in chili powder, salt and tomatoes. Remove from heat.
On ungreased large cookie sheet, unroll pie crusts. Spoon about 2 cups beef mixture onto half of each crust, spreading to within 1/2 inch of edge. Top each with 1/4 cup cheese.
Brush edge of each crust with beaten egg. Fold untopped half of each crust over filling; press edge with fork to seal. Cut slits in several places in top of each; brush with beaten egg.
Bake 20 to 25 minutes or until golden brown. Cut into wedges to serve.