Chicken Tostadas with Avocado Dressing

Avocado Dressing:

• 2 tbsp sour cream
• 2 tbsp chicken broth
• 2 tbsp lemon juice fresh
• 2 tsp vegetable oil
• salt to taste, sea salt and freshly cracked
• black pepper to taste, sea salt and freshly cracked
• ½ avocado ripe, peeled

Chicken Tostadas:

• 1 tbsp + 1 tsp vegetable oil divided
• ½ onion sliced, sweet yellow
• 2 cups chicken shredded, roasted
• ½ cup black beans rinsed and drained
• 4 flour tortilla or corn tortilla, small
• 1 cup romaine lettuce chopped
• 1 tomato diced
• ¼ cup cotija cheese crumbled