Granny's Cherokee Casserole

INGREDIENTS

• 1 pound lean ground beef
• 1 onion, finely diced
• 1 (10.75 ounce) can condensed cream of mushroom soup
• 1 cup instant rice
• 1 (14.5 ounce) can diced tomatoes
• 1 tablespoon garlic powder
• 1 teaspoon dried thyme
• 1 teaspoon dried oregano
• 2 teaspoons white sugar
• 6 slices American cheese