Combine flour, water and salt and kneed dough for 5-7 minutes. Split into two balls and cover and rest for 30 minutes.
Mince onion and pumpkin. Mix with salt, pepper and oil.
Melt butter in a pan.
Roll out one dough into a very thin sheet. Brush dough with melted butter.
Roll dough up like a scroll.
Roll second dough out into a thin sheet, brush with butter. Then wrap this sheet around the already scrolled dough.
Cut the scrolled dough tube into 12 pieces (like how you would prepare cinnamon rolls). Place pieces upright on a plate (so swirl is upright) and place in freezer for ten minutes in order to solidify the butter.
Take out of freezer and flatten dough pieces a bit. Then using a rolling pin, gently roll flat in a small circle. (you should be able to see a swirl pattern on the dough when it is rolled flat)
Place filling in the center of the dough and fold two edges together, then bring third edge into center to close and make the triangle shape.
Place egg in bowl and scramble with fork. This will be the egg wash.
Brush Samsa with egg wash and sprinkle with nigella seeds.
Bake for 20-30 minutes or until golden brown. Serve warm or room temperature.