Keto Cheeseburger Casserole

INGREDIENTS:

• 2 lbs extra lean ground beef
• 2 tsp coarse kosher salt not fine salt
• ¼ cup avocado oil mayonnaise
• ¼ tsp black pepper
• 1 tbsp minced garlic
• olive oil spray for the baking dish
• ¼ cup unsweetened ketchup
• 1 medium onion finely chopped
• 1 ½ cup shredded sharp cheddar divided
• 2 tbsp olive oil
• 1 tbsp mustard

DIRECTIONS: