- Prepare the grill for direct cooking over medium heat (350° to 450°F).
- Brush the cooking grates clean. Grill the tomatoes, onion, and peppers over direct medium heat, with the lid closed as much as possible, until the tomatoes and onions are soft and the peppers are blackened and blistered, turning every few minutes. The tomatoes and onions will take 8 to 10 minutes, and the peppers will take 10 to 15 minutes. Remove the vegetables from the grill as they are done. Place the peppers in a bowl and cover with plastic wrap to trap the steam. Let stand for about 10 minutes.
- When the vegetables are cool enough to handle, pull the skins from the tomatoes and cut out the stem ends. Peel, core, and seed the peppers. In the bowl of a food processor combine the tomatoes, onion, peppers, basil, oregano, garlic, vinegar, salt, and pepper. Pulse until a semi-smooth puree is created. With the motor running, slowly add the oil. In a medium saucepan over low heat, warm the puree until slightly thickened, 3 to 5 minutes, stirring occasionally. Remove from the heat.
- With the cut sides of the zucchini facing up, lightly score the flesh 1/8 to 1/4 inch in from the edges all the way around. Using a small spoon or melon baller, and using the scored edges as guides, carefully scoop out and discard the flesh and seeds, leaving what looks like a boat with uniformly thick walls.
- In a medium bowl gently combine the sausage meat, cheese, bread crumbs, and 1/2 cup of the puree. Divide the mixture evenly between the zucchini boats, spreading it and lightly pressing it to fill the shells completely.
- Brush the cooking grates clean. Grill the zucchini boats over direct medium heat, with the lid closed as much as possible, until the sausage is cooked through and no longer pink, about 15 minutes. Using a wide spatula under the zucchini for support, carefully remove them from the grill. Serve on a bed of rice or pasta, if desired, and top each with some of the warm puree. Pass any remaining puree.
Recipe from Time to Grill by Jamie Purviance/Sunset, 2011.