Thaw the puff pastry. Preheat oven to 400°. When thawed, if the pastry is a circle you can cut two sides off to place and tamp down on the remaining round ends to form a rectangle.
Slice the tomatoes about 1/4 to 1/2 inch thick. Sprinkle with sea salt and let them rest for 10-15 minutes between two sheets of paper towels to drain some of the liquid from the tomatoes. Spread the crème fraiche over the surface of the puff pastry. Then place the tomatoes in a nice pattern over the crème fraiche and sprinkle the herbs overall.
Slice the red onion as thinly as you can and place a thin scattered layer over the tomatoes, not too much.
Bake for 20-25 minutes in the oven, checking the evenness of the baking halfway through. As soon as your crust is browned evenly remove it from the oven. Immediately dot tablespoons of the cheese mixture over the surface of the tart. Drizzle the pesto and oil sauce over the tart and sprinkle with 1 tsp Aleppo peppers, if you like a little heat.
Finely slice a basil leaf or two and use the others for garnish. This tart is fabulous with a chilled glass of any of this week's rosés-all dry, crisp and flavorful!!