To make the stuffing, put the chopped onion, chopped salami, cubed provolone piquant, grated Parmigiano Reggiano, breadcrumbs, diced tomatoes, extra virgin olive oil and salt in a bowl and mix well. You may have to add more extra virgin olive oil, depending on the breadcrumbs and how much they absorb the liquids. You need to obtain a soft enough stuffing so that when you press it with your hands, it retains the shape you give it and doesn’t crumble. Keep it aside.