Preheat oven to 350°F.
Cook pasta according to package directions and drain.
Whisk together egg, half the salt, ¼ tsp garlic powder and ⅓ cup cheese.
Add pasta and toss.
Arrange in 9 inch pie dish, pressing to form shell.
Heat large skillet over medium heat until hot.
Add ground beef and brown 4-5 minutes, breaking up into ¾ inch crumbles.
Pour off drippings.
Season with remaining salt and remaining garlic powder.
Add cumin and stir in tomatoes (I used spaghetti sauce here).
Bring to a boil and cook 3-5 minutes or until liquid is almost evaporated, stirring occasionally.
Reserve 2 tbsp beef mixture for garnish.
Stir sour cream into remaining beef and spoon into pasta shell.
Place remaining cheese in center, leaving 2 inch border around edge.
Spoon reserved beef mixture onto center of cheese and bake 15 minutes or until heated through.