Preheat oven to 450F. Place red bell pepper on rack with cookie sheet on the rack below. Cook for about 30-40 minutes until skin is blistered and blackened.
Once cooked remove to glass bowl, cover with plastic wrap, allowing the pepper to steam and loosen the skin. Once cool enough to handle, peel skin off with your fingers.
While roasting the red pepper, in a pan on medium heat, fry your capocollo for a few minutes until lightly crisped.
In the same pan, place red onion, sauteing for about 1-2 minutes to lightly caramelize.
Butter the outside of each slice of bread.
On bottom slice, place half of your sliced roasted red pepper, the capocollo, red onions, lightly salt & pepper it, and top with shredded Gouda.
In a pan on medium heat, fry sandwich until golden brown and cheese is melted.