Place red peppers on to a baking sheet and place under hot broiler. Rotate the peppers as they char. Remove from oven, place into large bowl and cover with plastic wrap.
In a skillet over medium heat, melt butter. Saute onions 5 minutes and season with salt and pepper. Stir in garlic for another minute. Remove from the heat and set aside.
Remove peppers from bowl and peel blackened skin off completely. Cut peppers into chunks, removing the stem and seeds.
Place peppers, onions, garlic, cream cheese and mayonnaise into food processor and puree. Stir in salt and pepper to taste, pour into bowl and refrigerate until ready to serve.
Serve with vegetables, crackers or slices of bread.