In a food processor add the flour, sugar, salt, and baking powder and pulse to blend.
Add butter and pulse until grainy. Then add egg and pulse some more. Add 1 tbsp. of ice water to mix and pulse if dough isn't coming together.
Roll pastry dough on a floured surface until it is large enough to fit into a tart pan.
Place parchment or foil inside of tart pan and add pie weights to pan to keep the surface flat while baking.
Bake tart for 10 minutes at 350 degrees, remove pie weights and parchment and continue to bake for 7-10 more minutes.
Meanwhile, steam butternut squash in 400 degree oven for 20 minutes or until tender.