If using long sweet pepper: set them on the side that holds peppers stable and cut through the center leaving enough space on the side, top and bottom. Pull out the seeds and ribs. The cut-out center set aside.
If using sweet bell peppers: figure out 2 sides that will lay somewhat flat and stable and cut it in half. Pull out the seeds and ribs.
Steep couscous in hot water or hot vegetable stock. Cover with a plastic wrap or a lid and let sit for 10-15 minutes, then fluff it with a fork.
In the meantime prepare the veggies. Cut zucchini, tomato and pepper scraps in small cubes. In a saute pan add some extra virgin olive and garlic cloves crushed with a flat knife and vegetable cubes. Sautee for about 10 minutes until tender but stillwith a crunch to the veggies. Remove garlic cloves and let cool.
Add veggies to fluffed couscous together with flaked tuna, capers (optional) and chopped parsley. Mix gently.
Stuff peppers with couscous.
Arrange on a sheet pan lined with parchment paper.
Bake in a preheated to 350F oven for 20-30 minutes until peppers start to become slightly wrinkled. It’ll be easier to peel them if you choose too.