On a sheet of parchment paper, roll puff pastry into a 10”x10”square. Transfer the parchment paper and puff pastry to a rimmed baking sheet.
Dollop pesto in the center of the puff pastry and use a spoon to spread in an even layer leaving 1” border.
Place sliced havarti cheese in an even layer over the pesto.Arrange the sliced tomatoes on top of the cheese and then sprinkle with the cherry tomatoes. Fold the edge of the puff pastry up and over the edges of the tomatoes, overlapping at the corners.
Drizzle the top of the tart with olive oil and sprinkle with salt and pepper. Brush the edges of the puff pastry with beaten egg and bake for 25-30 minutes, until the puff pastry is deeply golden brown. Let cool slightly to set and then slice and serve.