I recommend using canned tomatoes as they tend to have a more consistent flavor than fresh tomatoes. I find that fresh tomatoes can be mealy in texture and are sometimes underripe. If you want to use fresh tomatoes you can. Simply peel the tomatoes by cutting an X in the bottom of each one, then place the tomatoes in boiling water for 30 seconds. Transfer the tomatoes to a bowl of ice water and let them sit for 5 minutes. The skins should easily peel off. After the tomatoes are peeled, coarsely chop them, then proceed with the recipe.