2 pounds center-cut skinless boneless salt cod (baccalà), rinsed well
2 tablespoons salt-packed capers*
7 tablespoons extra-virgin olive oil
1 medium onion, finely diced (about 1 1/2 cups)
4 1/2 teaspoons red pepper flakes
1 (28-ounce) can whole San Marzano tomatoes in juice
1 teaspoon kosher or coarse sea salt
1/4 cup fresh flat-leaf parsley, coarsely chopped
1/4 cup plus 1 tablespoon fresh mint, coarsely chopped
4-6