Mexican Enchilada Casserole

INGREDIENTS

• cooking spray
• 1 1/2 cups canned tomato sauce
• 1/3 cup chili powder (such as Gebhardt®)
• 1/2 cup water, or as needed
•  
• 1 1/2 pounds ground turkey
• 1 1/2 cups chopped onion
• 2 (1 ounce) packages taco seasoning mix, divided
• 2/3 cup water
• 16 (5 inch) corn tortillas, cut in half
• 3 cups shredded sharp Cheddar cheese
• 3 cups shredded Monterey Jack cheese
• 1 1/2 (10 ounce) bags shredded iceberg lettuce
• 2 cups chopped fresh tomatoes