Preheat the oven to 400ºF. Line a baking sheet with parchment paper.
Slice the heirloom tomatoes into 1/4-inch-thick rounds and place them on paper towels to drain.
Lightly flour your work surface then roll the thawed puff pastry into about a 10-by-14-inch rectangle. Transfer the puff pastry to the prepared baking sheet.
Spread the pesto onto the puff pastry, leaving a 1/2-inch border on all sides. Divide the goat cheese into dollops and scatter it on top of the pesto.
Arrange the sliced tomatoes on top of the goat cheese.
Bake the tart for about 12 minutes or until golden brown. Remove it and let it cool for 10 minutes.
Slice or tear the basil and scatter it atop the tart, then sprinkle the tart with sea salt and serve.