Combine all dressing ingredients in a blender or food processor and blend until smooth. Thin with water as needed to reach the desired consistency. Refrigerate until ready to serve.
Preheat gas grill or an indoor grill pan to medium high heat.
Brush corn with melted butter and cook until kernels are slightly charred, rotating one-quarter turn every few minutes until each side is done. Remove from heat and slice kernels from cob with a sharp knife. Reserve kernels and discard cobs.
In a large salad bowl combine lettuce, arugula, and cilantro.
In a medium bowl, combine diced bell pepper, red onion, black beans, roasted corn kernels, lime juice, and ground cumin. Season with salt and black pepper, to taste, and toss gently to combine.
Add the seasoned black bean mixture to the bowl with the chopped lettuce and toss gently to combine. Serve with Creamy Avocado Dressing and extra lime wedges.