Southwestern Salad With Avocado Dressing Tasty

Dressing
1 avocado, halved
1 clove garlic
½ teaspoon salt 
½ teaspoon pepper
¼ cup olive oil
1 tablespoon cilantro
1 lime, juiced

Salad
1 head of lettuce, chopped
1 cup bell peppers, chopped
¼ cup cilantro
15 ounces (1 can) black beans
½ cup red onion, chopped
15 ounces (1 can) corn 
¼ cup scallions
¾ cup tomatoes, chopped