Rinse and drain beans, puree in blender with mayonnaise and small amounts of water if needed to blend to a creamy consistency. Place in a bowl.
Saute diced onion in pan until caramel color, then add chopped garlic and saute a few minutes more.
Add chopped spinach to the onion and garlic. Saute until spinach is wilted and cooked down.
Season with salt and pepper.
Combine beans, spinach, artichokes, and grated cheese in a bowl.
Warm in the oven if you prefer this dip warm.