First, prepare ahead of time the peppers.
Wash the peppers and dry them with paper towel.
Place the peppers in a baking sheet.
Bake in a 400°F preheated oven for 15 to 20 minutes ( it may take longer if you have more peppers). Make sure to flip them over after the first 10 minutes of baking.
Peel off the outer skin.
Remove the seeds and internal ribs.
Cut the peppers lengthwise into strips.
Place in a bowl and season with salt.
Add olive oil (1 tablespoon or more). Set aside.
Prepare ahead of time the Caramelized onions, please see recipe link above.
Grate the Gouda cheese.
Now let’s assemble the sandwich.
Place a cast iron pan over medium heat.
Spread the butter on one side of each slice of bread.
Place each slice of bread on the cast iron pan ( butter side down)
Layer both slices of bread with the grated Gouda cheese( as much as you want).
Top the first slice with Caramelized onions and the second one with baked peppers.
Top both slices again with more grated Gouda cheese.
Using a spatula, gently place one loaded slice of bread on top of the other to sandwich it.
Gently press on top with a spatula for a minute or less.
Flip the sandwich over and let grill until golden brown.
Place in a plate and enjoy.