Bring the goat cheese to room temperature on the counter.
Slice the tomatoes then lay them out on a parchment paper lined baking sheet. Let them sit 10-15 minutes so some of the juices release.
Unroll the dough onto another parchment paper lined baking sheet. Carefully spread the goat cheese over the center area of the dough leaving about a 2” border all the way around. Top with half of the parmesan cheese.
Arrange the tomatoes over the top of the cheeses slightly overlapping, then season with salt and pepper and add the rest of the parmesan cheese.
Fold the dough over the tomatoes, pleating it, leaving the center exposed.
Whisk the egg and 1 tablespoon of water together, brush the crust with the egg wash and lay the thyme sprigs on top.
Bake at 400 degrees on the center rack 35-40 minutes or until the crust is flaky and golden then remove the thyme.
Let the tomato galette rest 15-20 minutes before cutting then remove the thyme and garnish with fresh sliced basil. *NOTE: don't worry if there's excess moisture when you take the galette out of the oven. It will absorb as it rests.