These are gorgeous nestled alongside a grilled or baked fish or a juicy steak or as the star of a vegetable plate. Medium-sized round tomatoes or large Romas work best, but cut Romas lengthwise in half instead of crosswise. Good-quality supermarket tomatoes work nicely because baking intensifies their flavor. Don't be tempted to use store-bought dry breadcrumbs here. Making fresh ones is so simple: Tear the bread into rough 2-inch pieces and buzz it in the food processor.
Preheat the oven to 425 degrees.
Arrange the tomatoes cut side up in a baking dish just large enough to hold them. Mix ½ teaspoon of the salt and the pepper in a cup and sprinkle over the tomatoes.
Melt the butter in a medium-sized skillet over medium heat. Brush a little butter over the cut side of each tomato, leaving some in the skillet. Bake the tomatoes, uncovered, until they are hot, begin to soften, and look juicy on top, 20-25 minutes.
Meanwhile, add the scallions and garlic to the butter remaining in the skillet. Cook over medium heat, stirring often, until the scallions are tender, about 2 minutes. Add the breadcrumbs and cook, stirring, until lightly golden and crisp, 3-5 minutes.
Scrape into a medium-sized bowl. Mix in the Parmesan, pecans, and remaining salt.
Spoon some of the crumb mixture atop each tomato half. Bake until the crumbs are browned and heated, 10-12 more minutes. Serve hot.