Heat oven to 375°. Coat a 9-inch cake pan with cooking spray
Trim off and discard the top 1/4 inch of each tomato. Working over a bowl, core and seed the tomatoes, reserving the pulp. Pick out and discard any hard pieces from the bowl.
In a medium bowl, stir together the remaining ingredients. Stir in 1/2 cup of the reserved tomato pulp.
Spoon the bread mixture into the tomatoes, distributing it evenly and mounding it slightly. Set the tomatoes in the prepared pan and bake for 30 minutes.