Mexican stack up

Ingredients

• 1 1/2 cups crushed tortilla chips
• 5 cheddar cheese slices
• 1 libra lean ground beef
• 1/2 teaspoon salt
• 1/2 teaspoon pepper
• 1/2 ground cumin
• 1 teaspoon chili powder
• 1 tablespoon taco seasoning
• 1 medium onion chopped, divided
• 1 garlic clove, minced
• 1 1/2 cups shredded lettuce
• 1 large tomato, diced
• 1 cup cheddar cheese, grated
• 1 avocado, sliced
• 1 pint sour cream