Using a mandoline on a medium setting, slice the beets, zucchini, and sweet potato.

Prebake the sweet potato slices; place on a microwave safe plate and microwave on high for three minutes or place in the oven at 350 degrees Fahrenheit for 15 minutes. Set aside.

Preheat the oven to 425 degrees Fahrenheit. Line a quarter-sheet pan with Gefen Parchment Paper.

Prepare the filling: In a medium bowl, whisk one egg, then stir in the basil. Add in the cream cheese and the feta cheese. Stir to combine. Set aside.

Unfold the puff pastry sheet and trim to fit the pan. Place dough into the parchment lined pan.

Using a knife, lightly score a line 3/4 inch from the edge of the pastry on each of the four sides.

Spoon the cheese mixture evenly on the puff pastry, inside of the scored lines.

Lay the sweet potato slices, overlapping, in two rows down the middle third of the cheese mixture. Repeat the process with the beets on one side and the zucchini slices along the last third of the tart. The vegetables should completely cover the cheese mixture.

Lightly brush or spray the vegetables with oil. Season with salt and pepper.

Beat the remaining egg. Brush the border of the dough with the beaten egg.

Once your tart is assembled, refrigerate it for 15 minutes before baking to prevent shrinking.

Bake until vegetables are tender and the crust is golden, about 25 to 30 minutes. Cool for five minutes, then use the parchment to slide the tart onto a board or platter. Serve warm or room temperature.