Line a rimmed baking sheet with paper towels. Arrange tomatoes on prepared baking sheet; sprinkle with salt and let stand for 30 minutes. Thoroughly pat dry.
Preheat oven to 400°. Line another rimmed baking sheet with parchment paper.
On a lightly floured surface, unroll pastry and roll into a 13×10-inch rectangle. Using a small sharp knife, score a ¾-inch border around rectangle; transfer to prepared baking sheet.
In a small bowl, stir together softened cheese, green onion, and Parmesan. Using a small offset spatula, gently spread cheese mixture over pastry, staying within border.
In a large bowl, whisk together oregano, oil, and rosemary; add tomatoes, tossing to combine. Arrange tomatoes over cheese mixture, overlapping slightly if needed. Brush egg over pastry border.
Bake until pastry is golden brown, 25 to 30 minutes. Let cool to room temperature. Garnish with Parmesan, oregano, rosemary, and green onion, if desired.
Notes
*We used Boursin Garlic & Fine Herbs Gournay Cheese.
Recipe by Southern Lady Magazine at https://southernladymagazine.com/heirloom-tomato-and-herb-tart-recipe/