The Classic California Cheeseburger - California Avocados

Ingredients

• 1 small white onion, peeled and thinly sliced
• 1/4 tsp. seasoned salt
• 1 Tbsp. butter, cut in small cubes
• 1 lb. ground beef (80% lean)
• 1/2 tsp. salt
• 1/8 tsp. ground pepper
• 4 (1-oz.) slices American or Cheddar cheese
• 4 sesame seed-topped burger buns, or your favorite buns/bread
• 4 medium iceberg or romaine lettuce leaves
• 1/4 cup mayonnaise or mustard, optional
• 1 ripe, Fresh California Avocado, seeded, peeled and sliced