Preheat oven to 400.
Place garlic and onion in an ovenproof pan and coat with olive oil.
Roast for 30 minutes or until garlic is golden, stirring half way through.
While the onions and garlic are roasting, place bell peppers (cut side down) and jalapeños on a rimmed baking sheet and put under the broiler until charred and completely black.
With tongs, carefully remove roasted peppers from the oven and place in a bowl. Cover with plastic wrap for 15 minutes.
After the roasted peppers have rested for 15 minutes, remove the skin and seeds.
Place tomatoes, roasted peppers, onions, garlic and salt in a blender or food processor and blend until smooth.
Combine 1 to 1 ½ cups of the pureed vegetables, yogurt and cream cheese in a bowl and mix well. Alternatively, you can use a blender.
Chill for at least 2 hours.