It's part of the flavor to cook the peppers with the lid on until blackened and softened. Berbere is a spice from Ethopia that my daughter Ariel introduced to me. It's a beguiling blend of chilies and about a dozen spices. I provide a link below to a recipe or look for Berbere at a spice shop.
Using a 9-10-inch skillet with lid, add oil to the skillet and heat over medium-high heat. Place peppers skin side down; cover and cook on medium-high heat, without turning peppers until skins are charred and flesh is very soft, about 20 minutes. You should hear sizzling as moisture condenses on the lid and drips into the pan.
When peppers are very soft with charred skins, add garlic and cook a few minutes to lightly toast the garlic. Remove pan from heat and cool slightly.
Place peppers (with skin) and garlic, walnuts and pomegranate molasses or lemon juice in a blender or food processor. Whirl until smooth and creamy-red color and is a spreadable consistency. Add a little olive oil to thin if needed. Season with salt, pepper, and berbere or red pepper flakes. Adjust pomegranate molasses and/or lemon juice for a little tangy-ness. Keeps refrigerated up to a week.