Preheat oven to 350 degree F.
Line a rimmed cookie sheet with parchment paper.
Slice tomatoes and set aside.
Pour olive oil into a small bowl.
Sprinkle some of the brown sugar onto a plate, you want to add a little at a time and work in stages.
Now take your first slice of tomato and dunk it into the olive oil, get both sides coated.
Now take that same tomato and press both sides of it onto the place with brown sugar so it evenly coats the tomato.
Place the tomato on the cookie sheet and continue until all the tomatoes are coated. You should end up with about 20 slices which fits nicely onto a large cookie sheet.
Place in the oven and cook for about 1 hour, checking occasionally to make sure they don't over brown. How fast they cook will vary slightly on the thickness of your slices.
After 1 hour you can flip them over and cook them for another 30 minutes. I would suggest you start to check after the 15 minute mark to be sure you don't over brown them.
Once they are caramelized nicely take them out and allow them to cool.
If you are not using them that day you can refrigerate them till you need them.