Pre-heat oven to 450° F.
Line an oven-safe dish or pan with tin foil and spray lightly with cooking spray.
Cut the tomatoes in half crosswise. Using a small spoon, scoop out the seeds and juice, leaving the inner membranes. Turn cut-side down to allow further draining of juices.
Mix the remaining ingredients, adding a generous amount of ground pepper.
Salt to taste.
Toss well to ensure everything is evenly distributed.
Drizzle 1/4 teaspoon of balsamic vinegar into the empty cavities in each tomato half.
Sprinkle some salt over the tomatoes.
Fill first the cavities of the tomatoes, and then top the tomatoes with the remaining filling so that they have a shallow dome of filling on top.
Press lightly to shape and keep the filling in place, but without packing the filling too tightly.
Bake for 20 minutes until the tomatoes are tender and the filling is golden brown on top. Cover lightly with a sheet of tin foil in the last few minutes, if necessary, to prevent burning the outer crust.