Apple Avocado Salad with Tangerine Dressing

• 1 (10 ounce) package baby greens
• 1/4 cup chopped red onion
• 1/2 cup chopped walnuts
• 1/3 cup crumbled blue cheese
• 2 teaspoons lemon zest
• 1 apple, peeled, cored and sliced
• 1 avocado, peeled, pitted and diced

For the dressing:

• 4 mandarin oranges, juiced
• 1/2 lemon, juiced
• 1/2 teaspoon lemon zest
• 1 clove garlic, minced
• 2 tablespoons olive oil
• salt to taste