Preheat the oven to 400°F (200°C).

Using a sharp paring knife, trim off the tops of the peppers, about 1/2-inch below the base. Scrape away any inner seeds and membranes. Place the peppers in a colander and rinse well under cold running water. Remove and roughly chop 5 of the peppers into small pieces and set the rest aside to drain.

In the bowl of a food processor, combine the tuna, reserved oil, capers, olives, garlic, and half of the tomatoes. Pulse until the ingredients are smooth. Sprinkle in the bread crumbs, parmigiana, and olive oil and pulse until well combined. Add the chopped peppers and remaining tomatoes and pulse briefly just to combine. Or else, you can use a hand blender to combine the ingredients in a large bowl, if you prefer.

Using a cookie making gun or a pastry bag, fitted with a wide round tip, fill the peppers with the stuffing. Smooth the surface of the stuffing and place the peppers on a lightly oiled baking sheet. Sprinkle the surface of the peppers with bread crumbs and parmigiana. Grate some caciocavallo cheese over the top and drizzle with a little olive oil.

Place the baking sheet in the oven and bake until the peppers are lightly charred and beginning to collapse, about 15 to 20 minutes. 


Serve hot, warm, or at room temperature.