Preheat oven to 425 F degrees.
On a lightly floured surface, lay the thawed sheet of puff pastry, dusting with enough flour to prevent it from sticking to the counter or rolling pin. Roll pastry out until it’s just big enough to fit your tart pan, coil the pastry onto the rolling pin to help you transfer it, then uncoil it onto the tart pan. Trim off any excess crust.
Prick the base all over with a fork to allow steam to escape and pie weights or dried beans so the pastry won't puff up excessively. Spread evenly.
Make an egg wash by combining 1 egg with 1 tablespoon of water. Brush sides of puff pastry and bake in oven for 15min. Lower temperature to 400 F degrees and set aside.
Meanwhile, finely grate ginger on a micro plane or mince. Combine ricotta, honey, ginger, lemon juice and zest, and a pinch of salt in the bowl of a food processor. Lightly beat the eggs in a small bowl and slowly add to the bowl of the food processor, while the motor is running.
Pour ricotta ginger filling into the parbaked puff pastry tart. Use the back of a spoon or a spatula to smooth the surfaces.Cut and measure rhubarb stalks so the pieces will fit into your tart pan. Top ricotta puff pastry with cut up rhubarb stalks.
Melt butter in a small sauce pan on the stove and mix in honey. Brush rhubarb stalk with honey butter mixture.
Bake tart at 400 F degress for 35 minutes, until almost set, brushing the rhubarb stalks with the honey-butter mixture every 10min or so.
Chop pistachios, top rhubarb tart with pistachio and bake an additional 5-10 minutes, until completley set.