In a food processor or blender, purée chickpeas, tahini, lemon juice, yogurt and oil until smooth, adding water as needed to make a creamy mixture. Transfer purée to a medium bowl.
Add garlic, cumin, cayenne, jalapeño and bell pepper. Mix well. Season with salt and pepper.
Cover and chill 2 to 4 hours to allow the flavors to blend. Garnish with cayenne pepper just before serving