Preheat the oven to 400ºF.
Using a sharp paring knife, cut out the cores of the tomatoes. Slice each tomato in half horizontally and scoop out the seeds. Place the halves cut-side up in a 13 x 9-inch rimmed baking sheet or casserole dish.
In a small bowl, mix together the garlic powder and salt and sprinkle the mixture evenly over the tops of the tomatoes.
In a separate bowl, mix together the breadcrumbs, olive oil, oregano, parsley, and sesame seeds until crumbs form. Spread this mixture evenly over the tops of the tomatoes.
Bake the tomatoes for 20 to 25 minutes, until they are tender enough to be pierced easily with a fork but still hold their shape. Serve hot.