Wash the tomatoes, then cut them in half along their widest point.
Add 2 tbsp olive oil to the bottom of a baking dish. Arrange the tomato halves, cut side up, within the dish. They can be squeezed in, since they will shrink during cooking.
Sprinkle the tops evenly with parsley, garlic, salt, and pepper.
Pour the remaining olive oil on top.
Place the dish in the oven on the upper racks and cook for at least one hour.
You will know the tomatoes are done when they have shrunk to almost half their size, the liquid in the pan is nearly gone, and the edges of the tomatoes are blackened and look deflated.