Preheat oven to 425 degrees.
Combine the ricotta cheese, scallions, parsley, basil, and lemon zest in a small bowl. Set aside. (Can stay at room temperature.)
Place the cherry tomatoes on a baking sheet. Drizzle with the olive oil and sprinkle with salt and black pepper to taste. Roast for 12-15 minutes or until beginning to soften and burst.
Meanwhile, unfold the puff pastry onto a lightly floured piece of parchment paper. Gently roll it out to smooth the creases and flatten it slightly. Place it onto a large rimmed baking sheet.
Using a straightedge, score the pastry approximately 1/2 inch to 1 inch from the edge, being careful not to cut all the way through. Brush the entire crust with the beaten egg.
Bake for 15-17 minutes or until golden brown. Reduce the oven temperature to 350 degrees.
Pierce the center of the baked crust with a paring knife in several places and apply light pressure with a spatula or another kitchen utensil, and gently deflate it. (It will take a little time. Be careful not to damage the crust.) Let the crust cool to the touch.
Working with approximately 1 heaping tablespoon at a time, drop the ricotta cheese mixture onto the center of the crust and carefully spread it around.
Top with the cherry tomatoes and some of the juices (don't overdo it).
Return the tart to the oven for 10 minutes.
Sprinkle with thinly sliced basil (chiffonade). Drizzle with good-quality balsamic vinegar and cut into 4 pieces. Serve immediately.