Preheat the oven to 425 degrees F. Line a baking sheet with parchment paper or foil.
Place a sheet of puff pastry on the baking sheet. Poke holes all over the puff pastry with a fork. Brush the entire thing with the egg wash. Sprinkle the edges of the sheet with the everything seasoning.
Bake the puff pastry for 20 to 25 minutes, until it’s golden brown and puffy, If it’s puffed up a lot in the center, you can poke it with a fork to deflate it a bit.
Let the pastry cool slightly. Gently spread the cream cheese over the tart. This will be tricky because it will lift a few flakey bits from the top of the pastry, but that’s okay! That’s why it is important to use whipped cream cheese - it is light and fluffy and not as heavy as the non-whipped cream cheese.
Layer the smoked salmon on top of the cream cheese. Sprinkle on the pickled onions, fresh dill, capers and another pinch of everything seasoning. Add on a squeeze of fresh lemon. Slice and serve!