You can use any white flaky fish in this recipe....use what is local for you. I tend to use Amberjack, grouper or snapper. Basically whatever my neighbor caught that day! I can't vouch for the flavor with a heavier fish like tuna or salmon. But feel free to try it. This recipe can be grilled (use heavy duty foil) or baked (use parchment paper).
hoose your cooking method, and select the correct vessel for your dish -- foil or parchment paper. Place four 14x12" sheets of foil (grill) or parchment paper (baking) on a work surface. Divide the squash among the parchment paper or foil, arranging on one side of the sheet in thin layers. Sprinkle the shallots and sliced basil over, dividing equally. Scatter the tomato halves around the squash. Drizzle each packet with 1 tbsp wind and 1/2 tbs oil. Add 1/2 tbsp water to each packet if grilling. Season with salt and pepper. Place a fish fillet atop each portion. Season with salt and pepper; drizzle 1/2 tbsp oil over each.
Fold the foil or parchment paper over the mixture and crimp the edges tightly to form a sealed packet. (This can be made 4 hours ahead. Keep refrigerated. Let stand at room temperature for 15 minutes before continuing cooking.).
Build a medium fire in a charcoal grill or heat a gas grill to medium-high. Alternately, heat the oven to 400 degrees. Bake or grill the fish until just cooked through (A toothpick poked through the parchment paper will slide through fish easily.) about 10 minutes.
Carefully cut open the packets (steam will escape). Garnish with the basil leaves.